English

• 1.   Introduction

  Given the prominence of fluorine effect in pharmaceutical, agrochemical, and materials industries, the construction of fluorine-containing compounds has attracted a great deal of attention from synthetic chemists in recent years.^[1] In this regard, monofluoroalkenes, a typical representative of fluorinated compounds regarding as nonhydrolyzable amide bioisosteres in medicinal chemistry (Figure 1), ^[2] are of great significance due to their higher metabolic and conformational stability, increased lipophilicity, and better recognition.^[3] Moreover, they also serve as versatile synthetic precursors for organofluorine synthesis.^[4] Among the numerous methods for multisubstituted monofluoroalkenes synthesis, ^[5] only scattered examples were known to access the thermodynamically less stable E-monofluorostil- benes.^[6-10] These include Wittig reactions (Scheme 1a), ^[6] transition-metal-catalyzed cross-coupling of stereodefined alkenyl halides with different organometallic nucleophiles (Scheme 1b), ^[7] base promoted β-halo elimination of vicinal dihalides (Scheme 1c), ^[8] and electrophilic fluorination of alkenyl borons^[9a] and silicons^[9b] (Scheme 1d). Alternatively, manganese catalyzed α-fluoroalkenylation of arenes with gem-difluoroalkenes through C—H/C—F bond activations was also feasible to synthesize E isomer, with optimal 76:24 E stereoselectivity being observed (Scheme 1e).^[10] Nevertheless, limitations from these strategies such as poor control of stereoselectivity, the use of higher energy reagents, the need for prefunctionalization of substrates, and low step economy still exist. Therefore, it is highly desirable to develop new synthetic methodology for the realization of such important molecules.

  Figure 1

  

  Figure 1.  Selected bioactive monofluoroalkenes

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  Scheme 1

  

  Scheme 1.  Different approaches toward E-monofluorostilbenes and photocatalytic isomerization of alkenes

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  Pioneered by Hammond, ^[11] and later advanced by the groups of Arai, ^[12] Gilmour, ^[13] Weaver, ^[14] and others, ^[15] photo-mediated isomerization of the more readily accessible alkenes has proven to be an efficient strategy for the buildup of thermodynamically less stable alkenes (Scheme 1f).^[16] Thus, with the aid of suitable photosensitizers (organocatalysts or metal-based complexes), a selective energy transfer (EnT) is more favorable to thermodynamically stable alkene, resulting in accumulation of its isomer via a transient, high-energy excited triplet-biradical species.^[17] For example, Gilmour's elegant Z-selective photoisomerization of activated olefins catalyzed by natural riboflavin^[13a-13b] and Weaver's allylamines photoisomerization under iridium catalysis^[14a] beautifully exemplify this notion. Interestingly, in all these cases, few fluorinated alkene substrates were explored and lower yields or stereoselectivities were observed.^[13a-13d] In connection with our continuous interest in constructing Z-monofluoroalkenes, ^[18] We are eager to develop a straightforward method for accessing the synthetically challenging E isomers. Herein, we report our realization of an iridium(Ⅲ)-catalyzed Z→E isomerization of monofluorostilbenes under visible-light irradiation and mild reaction conditions (Scheme 1g). The reaction leads to the facile and straightforward synthesis of thermodynamically less stable E-monofluorostilbenes with good functional groups tolerance, good to excellent yields, and synthetically useful ratios. Furthermore, the synthetic utility of this method is demonstrated by the rapid synthesis of monofluorinated bioactive cis-DMU-212 analogue E-30.

  2.   Results and discussion

  At the outset the photoisomerization of monofluorostilbene Z-1 to E-1 was investigated (Table 1). With a household blue LED as the visible light source, the transformation was found to be effective in acetonitrile with different photosensitizers. Compared to small molecule organocatalysts, metal-based complexes were more efficient (Entries 1~8). With 1 mol% catalyst loading, iridium-based complex B with 221.8 kJ/mol E_T energy showed good reaction efficiency and led to a synthetically useful ratio (Entry 6, E:Z=82:18). The solvent screening revealed that no further improvement was observed by changing the reaction medium to EtOAc, ethanol, or tetrahydrofuran (Entries 9~11). Remarkably, the presence of water and air did not affect the reactivity, adding to the operational simplicity of the protocol (Entries 12, 13). Control experiments showed that both the photocatalyst and visible light were essential for this transformation, which suggested a visible-light promoted photo-sensitization pathway involving in the reaction (Entries 14, 15).

  Table 1

  

  Table 1.  Optimization of the reaction conditions^a

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  Entry	Photocatalyst	ET/(kJ•mol-1)b	Solvent	E:Zc
  1d	Benzil	223.4	MeCN	47:53
  2d	Fluorenone	223.0	MeCN	59:41
  3d	(—)-Riboflavin	209.2	MeCN	18:82
  4	A	252.7	MeCN	76:24
  5	Ir(ppy)3	235.6	MeCN	78:22
  6	B	221.8	MeCN	82:18
  7	C	215.1	MeCN	71:29
  8	[Ru(bpy)3]Cl2	205.0	MeCN	75:25
  9	B	221.8	EtOAc	78:22
  10	B	221.8	EtOH	77:23
  11	B	221.8	THF	75:25
  12e	B	221.8	MeCN	80:20
  13f	B	221.8	MeCN	80:20
  14	—		MeCN	< 1:99
  15g	B	221.8	MeCN	< 1:99
  a General reaction conditions: 18 W blue LEDs, Z-1 (0.1 mmol, 1.0 equiv.), photocatalyst (0.001 mmol, 1 mol%), solvent (2.0 mL), air, r.t., 10 h. b ET: Triplet state energy. c Determined by 1H NMR spectroscopy of the crude product. d 5 mol% catalyst loading was employed. e 1 drop of water was added. f Conducted under argon atmosphere. g Performed in darkness.

  With the optimized conditions in hand (Table 1, Entry 6), the substrate scope and limitations of the photoisomerization reaction were investigated. As illustrated in Table 2, the transformation was found to be very general and robust to a series of monofluorostilbene derivatives. Commonly encountered substituents, regardless of the electronic nature, at different positions of both benzene rings were well tolerated, giving the corresponding products with high yields and generally good E-alkene conversion (E-1-24). Functional groups such as ether, halides (E-1, 6, 8, 11, 13, 14, 21, 24), trifluoromethyl (E-3, 5, 7, 8, 18, 20), ^[19] acetyl (E-16), and ester (E-17, 23) were valuable functional handles for further derivatization. In addition, more substituents on either Ar¹ or Ar² ring did not hamper the reactivity (E-8, 10, 20, 24). It is worthy of note that an improvement in the geometric rations was observed when installing two groups both at the ortho-position (E-21-23, E:Z > 85:15). This result may be attributed to the increased triplet excitation energy of the E-isomers caused by their severely congested and highly twisted conformation, whereas there is nearly no influence for the triplet excitation energy of the Z-isomers due to their relatively planar conformation. However, a decreased level of selectivity for dichloro substrate Z-24 was observed. This outcome is presumably originated from the sterical hindrance-caused deconjugation of the raw material E-24since it compromises the efficiency of the initial energy transfer from excited state catalyst to substrate.^{[13, 15d-e, 16b]} Gratefully, the reaction was not limited to phenyl system; heterocyclic aromatic substrates such as thiophene (E-25), pyridine (E-26), and indole (E-27) were well tolerated with good efficiency. The successful isomerization of compound Z-27 suggested that this protocol is complementary to the metal-catalyzed C—H/C—F bond activation for the synthesis of stereodefined monofluoro- stilbenes.^[20] It is noted that the 5-membered-ring containing substrates (Z-25, 27) lead to relatively low selectivities as both the Z- and E-isomers are planar and fully conjugated.^{[16b, 21]} Unfortunately, the current reaction conditions were not compatible with the alkyl substituted alkene. For example, the use of isopropyl, cyclohexyl, or t-butyl substituted monofluorostyrene derivatives only gave trace of the isomerized products (not shown). Similarly, 1, 2-di- and tetra-substituted monofluoroalkenes exhibited lower isomerization reactivity. It was worth noting that although the overall yields and geometric rations were given in Table 2, all of the E-monofluorostilbenes could be separated with their Z-isomers by column chromatography.

  Table 2

  

  Table 2.  Substrate scope of the photoisomerization reactions

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  a Isolated yield. E:Z ratio was determined by 1H NMR spectroscopy analysis. b 5 mol% benzil was used instead of cat. B.

  The synthetic utility of this photoisomerization reaction was demonstrated by a rapid synthesis of monofluorinated cis-DMU-212 analogue E-30 (Scheme 2a). DMU-212 is a potent anticancer agent which shows preferential growth- inhibitory and proapoptotic properties in transformed cells.^[22] Suzuki-Miyaura type cross-coupling reaction of gem-difluoroalkene 28 with arylboronic acid 29 under Cao's nickel catalysis conditions^[23] successfully provided Z-30, which was then photoisomerized to E-30 under our conditions in 87% yield and 71:29 geometric selectivity.

  Scheme 2

  

  Scheme 2.  Synthetic utility and plausible mechanism

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  On the basis of the results obtained and preceding reports about the photocatalytic isomerization of alkenes, ^[11-16] a selective triplet energy transfer^[24] mechanism is tentatively illustrated in Scheme 2b. Initially, the ground state Ir(Ⅲ) complex accepts a photon from the visible light source and is followed by intersystem crossing (ISC) to generate the excited triplet state photosensitizer [Ir(Ⅲ)]*. Thereafter, the selective EnT from the photoexcited catalyst to Z-mono- fluorostilbene (see Stern-Volmer photoquenching experiments in Supporting Information) leads to a delocalized biradical intermediate triplet stateZ-Int, ^[13a] which is readily in equilibrium with Int and E-Int via the C—C single bond rotation. Finally, E-Int and Z-Int can undergo ISC with dissipation of energy to give localized E- and Z-iso- mers, respectively. The E-isomers usually have higher triplet excitation energy than Z-isomers because of the deconjugation effected by their severely congested and highly twisted conformation. Thus, the accumulation of E-isomer might be caused by the inefficient EnT from [Ir(Ⅲ)]* to itself.

  3.   Conclusions

  In summary, we have developed a visible light-promoted stereoselectively photocatalytic isomerization of monofluorostilbenes for the preparation of thermodynamically less stable E isomers. The reaction is remarkably clean and proceeds under mild reaction conditions, with good functional groups tolerance and synthetically useful yields and ratios. Finally, a triplet energy transfer pathway is tentatively proposed and the synthetic utility of this method is demonstrated by the rapid synthesis of monofluorinated cis-DMU-212 analogue E-30.

  4.   Experimental section

  4.1   General experimental information

  Unless otherwise stated, all regents and solvents were purchased from commercial suppliers and used without further purification. No attempts were made to optimize yields for substrate preparation. Proton (¹H), fluorine (¹⁹F), and carbon (¹³C) NMR spectra were recorded on a 400 or 500 MHz spectrometer (400 or 500 MHz for ¹H, 376 or 471 MHz for ¹⁹F, and 101 or 126 MHz for ¹³C, respectively). CDCl₃ was used as the NMR solvents. ¹⁹F NMR was reported as 19F exp. no decoupling (F19) unless otherwise noted. High-resolution mass spectra (HRMS) were recorded on a Bruker VPEXII spectrometer with EI and ESI mode unless otherwise stated, and the mass analysis mode of HRMS was TOF.

  Photocatalytic reactions were performed on a photoreactor (model: WP-TEC-1020HSL, manufactured by WAT- TCAS) with household blue LED (18 W).

  4.2   Preparation of Z-monofluorostilbenes

  (Z)-1-Fluoro-4-(1-fluoro-2-(4-methoxyphenyl)vinyl)- benzene (Z-1): Z-1 was prepared (82% yield as a white solid) according to the known method.^[18c] The data is consistent with the literature report.^[23] m.p. 100~104 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 7.67~7.48 (m, 4H), 7.09 (t, J=8.8 Hz, 2H), 6.92 (d, J=9.0 Hz, 2H), 6.19 (d, J=39.7 Hz, 1H), 3.84 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -112.48, -116.41 (d, J=39.5 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 162.9 (d, J=248.4 Hz), 158.8 (d, J=3.2 Hz), 155.2 (d, J=255.7 Hz), 130.2 (d, J=7.7 Hz), 129.4 (d, J=28.6 Hz), 126.2 (d, J=3.2 Hz), 125.9 (t, J=7.7 Hz), 115.6 (dd, J=21.4, 2.5 Hz), 114.1, 105.2 (dd, J=11.3, 2.5 Hz), 55.3. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0852.

  (Z)-1-(2-Fluoro-2-phenylvinyl)-4-methoxybenzene (Z-2): Z-2 was prepared (67% yield as a pale yellow oil) according to the known method.^[18c] The data is consistent with the literature report.^{[25] 1}H NMR (400 MHz, Chloroform-d) δ: 7.66~7.56 (m, 4H), 7.40 (t, J=7.7 Hz, 2H), 7.37~7.30 (m, 1H), 6.92 (d, J=8.9 Hz, 2H), 6.27 (d, J=39.9 Hz, 1H), 3.84 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -117.11 (d, J=39.5 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 158.8 (d, J=3.2 Hz), 156.0 (d, J=255.7 Hz), 133.1 (d, J=27.7 Hz), 130.3 (d, J=7.7 Hz), 128.6 (d, J=4.5 Hz), 128.5, 126.4 (d, J=3.2 Hz), 124.0 (d, J=7.3 Hz), 114.1, 105.4 (d, J=10.9 Hz), 55.3.

  (Z)-1-(2-Fluoro-2-(4-(trifluoromethyl)phenyl)vinyl)-4- methoxybenzene (Z-3): Z-3 was prepared (85% yield as a pale yellow oil) according to the known method.^[18c] The data is consistent with the literature report.^{[23] 1}H NMR (400 MHz, Chloroform-d) δ: 7.97 (dd, J=7.8, 1.7 Hz, 1H), 7.77 (d, J=8.2 Hz, 2H), 7.66 (d, J=8.3 Hz, 2H), 7.34~7.27 (m, 1H), 7.03 (t, J=7.6 Hz, 1H), 6.95~6.91 (m, 1H), 6.93 (d, J=40.5 Hz, 1H), 3.90 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -62.64, -117.07 (d, J=40.8 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 156.7, 155.7 (d, J=257.5 Hz), 136.7 (d, J=28.6 Hz), 130.4 (q, J=32.6 Hz), 130.1 (d, J=13.9 Hz), 129.2 (d, J=2.2 Hz), 125.8~125.2 (m), 124.4 (d, J=7.3 Hz), 124.0 (q, J=271.6 Hz), 121.9 (d, J=3.7 Hz), 120.8, 110.5, 101.6 (d, J=8.4 Hz), 55.6.

  (Z)-4, 4'-(1-Fluoroethene-1, 2-diyl)bis(methoxybenzene) (Z-4): Z-4 was prepared (71% yield as a pale yellow oil) according to the known method.^[18c] The data is consistent with the literature report.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.56 (dd, J=8.9, 3.5 Hz, 4H), 6.92 (dd, J=9.0, 6.7 Hz, 4H), 6.13 (d, J=40.1 Hz, 1H), 3.84 (d, J=4.8 Hz, 6H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -116.14 (d, J=40.2 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 160.0, 158.5 (d, J=3.2 Hz), 156.1 (d, J=254.8 Hz), 130.0 (d, J=8.2 Hz), 126.8 (d, J=3.2 Hz), 125.8 (d, J=28.2 Hz), 125.5 (d, J=7.3 Hz), 114.0, 103.7 (d, J=10.9 Hz), 55.3 (d, J=10.9 Hz).

  (Z)-1-(2-Fluoro-2-phenylvinyl)-4-(trifluoromethyl)ben- zene (Z-5): Z-5 was prepared (87% yield as a white solid) according to the known method.^[23] The data is consistent with the literature report.^[6c] m.p. 101~107 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 7.74 (d, J=7.3 Hz, 2H), 7.67 (d, J=7.6 Hz, 2H), 7.62 (d, J=6.9 Hz, 2H), 7.47~7.39 (m, 3H), 6.35 (dd, J=38.7, 2.4 Hz, 1H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -62.59, -111.03 (d, J=38.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 158.7 (d, J=262.1 Hz), 137.2, 132.2 (d, J=27.7 Hz), 129.7, 129.0 (d, J=8.2 Hz), 128.7 (d, J=2.3 Hz), 125.8~125.2 (m), 124.6 (d, J=7.3 Hz), 124.2 (q, J=272.3 Hz), 104.6 (d, J=10.4 Hz). HRMS (EI) calcd for C₁₅H₁₀OF₄ 266.0713, found 266.0712.

  (Z)-1-Chloro-3-(1-fluoro-2-(4-methoxyphenyl)vinyl)benzene (Z-6): Z-6 was prepared (50% yield as a white solid) according to the known method.^[18c] m.p. 79~83 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 7.59 (d, J=9.2 Hz, 3H), 7.53~7.47 (m, 1H), 7.35~7.30 (m, 2H), 6.92 (d, J=8.9 Hz, 2H), 6.27 (d, J=39.6 Hz, 1H), 3.84 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -117.70 (d, J=39.5 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 159.1 (d, J=3.2 Hz), 154.5 (d, J=255.7 Hz), 134.9 (d, J=28.6 Hz), 134.7 (d, J=2.3 Hz), 130.5 (d, J=7.7 Hz), 129.8 (d, J=2.3 Hz), 128.5, 125.9 (d, J=3.2 Hz), 124.0 (d, J=8.2 Hz), 122.0 (d, J=7.3 Hz), 114.1, 106.6 (d, J=10.4 Hz), 55.3. HRMS (EI) calcd for C₁₅H₁₂OFCl 262.0555, found 262.0555.

  (Z)-1-(1-Fluoro-2-(4-methoxyphenyl)vinyl)-3-(trifluo- romethyl)benzene (Z-7): Z-7 was prepared (75% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.97 (dd, J=7.8, 1.8 Hz, 1H), 7.93 (s, 1H), 7.87 (d, J=7.8 Hz, 1H), 7.62 (d, J=7.7 Hz, 1H), 7.55 (t, J=7.8 Hz, 1H), 7.35~7.26 (m, 1H), 7.04 (t, J=7.6 Hz, 1H), 6.96~6.94 (m, 1H), 6.89 (d, J=36.6 Hz, 1H), 3.92 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -62.80, -116.92 (d, J=40.7 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 156.6, 155.6 (d, J=257.4 Hz), 134.2 (d, J=29.0 Hz), 131.1 (dd, J=32.5, 2.3 Hz), 130.1 (d, J=13.9 Hz), 129.1, 129.1, 127.4 (d, J=6.6 Hz), 125.6~124.7 (m), 122.6, 121.9 (d, J=3.7 Hz), 121.1 (dd, J=7.9, 3.9 Hz), 120.8, 110.5, 101.0 (d, J=8.4 Hz), 55.6. HRMS (EI) calcd for C₁₆H₁₂OF₄ 296.0819, found 296.0817.

  (Z)-1-Chloro-4-(1-fluoro-2-(4-(trifluoromethyl)phenyl)- vinyl)-2-methylbenzene (Z-8): Z-8 was prepared (87% yield as a pale yellow oil) according to the known method.^{[23] 1}H NMR (500 MHz, Chloroform-d) δ:7.71 (d, J=8.2 Hz, 2H), 7.62 (d, J=8.4 Hz, 2H), 7.52 (d, J=2.1 Hz, 1H), 7.44~7.36 (m, 2H), 6.30 (d, J=38.6 Hz, 1H), 2.43 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -62.63, -111.14 (d, J=38.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 157.9 (d, J=261.1 Hz), 137.0, 136.6 (d, J=1.8 Hz), 135.8, 130.7 (d, J=27.7 Hz), 129.4 (d, J=2.3 Hz), 129.0 (d, J=8.2 Hz), 126.9 (d, J=7.7 Hz), 128.9 (qd, J=32.0, 2.6 Hz), 125.5 (q, J=4.1 Hz), 124.1 (q, J=273.37 Hz), 123.2 (d, J=7.7 Hz), 104.9, 20.2. HRMS (EI) calcd for C₁₆H₁₁F₄Cl 314.0480, found 314.0481.

  (Z)-1-(1-Fluoro-2-(4-methoxyphenyl)vinyl)-2-methyl- benzene (Z-9): Z-9 was prepared (45% yield as a pale yellow oil) according to the known method.^[18c] The data is consistent with the literature report.^{[23] 1}H NMR (400 MHz, Chloroform-d) δ:8.00 (d, J=7.8 Hz, 1H), 7.61~7.47 (m, 1H), 7.36~7.24 (m, 4H), 7.05 (t, J=7.5 Hz, 1H), 6.94 (dd, J=8.3, 1.2 Hz, 1H), 6.44 (dd, J=39.6, 1.5 Hz, 1H), 3.88 (s, 3H), 2.53 (d, J=3.5 Hz, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -99.15 (d, J=39.9 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 158.7 (d, J=263.0 Hz), 156.4, 136.7, 133.7 (d, J=25.7 Hz), 130.8, 129.8 (d, J=13.2 Hz), 129.2, 128.9 (d, J=5.1 Hz), 128.5 (d, J=2.2 Hz), 125.7, 122.7 (d, J=4.0 Hz), 120.7, 110.6, 103.5 (d, J=9.2 Hz), 55.6, 20.8 (d, J=4.0 Hz).

  (Z)-1-(1-Fluoro-2-(4-methoxyphenyl)vinyl)-2, 4-dime- thylbenzene (Z-10): Z-10 was prepared (56% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (500 MHz, Chloroform-d) δ: 7.95 (d, J=7.7 Hz, 1H), 7.39 (d, J=7.7 Hz, 1H), 7.27~7.21 (m, 1H), 7.09~6.97 (m, 3H), 6.91 (d, J=8.2 Hz, 1H), 6.36 (d, J=39.6 Hz, 1H), 3.85 (s, 3H), 2.45 (d, J=3.5 Hz, 3H), 2.36 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -98.69 (d, J=39.0 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 158.8 (d, J=262.6 Hz), 156.4, 139.2, 136.5, 131.6, 131.0, 130.8, 129.8 (d, J=13.2 Hz), 128.9 (d, J=5.1 Hz), 128.3 (d, J=2.2 Hz), 126.4, 122.8 (d, J=4.0 Hz), 110.6, 103.0 (d, J=9.2 Hz), 55.6, 21.2, 20.7 (d, J=4.0 Hz). HRMS (EI) calcd for C₁₇H₁₇OF 256.1258, found 256.1259.

  (Z)-1-(2-Fluoro-2-(4-fluorophenyl)vinyl)-3-methoxy- benzene (Z-11): Z-11 was prepared (45% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (500 MHz, Chloroform-d) δ: 7.64 (tt, J=7.8, 1.8 Hz, 1H), 7.35~7.24 (m, 2H), 7.24~7.19 (m, 3H), 7.17~7.10 (m, 1H), 6.88~6.82 (m, 1H), 6.50 (d, J=41.2 Hz, 1H), 3.84 (d, J=1.7 Hz, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -109.58 (dd, J=41.2, 9.1 Hz), -110.70~-113.39 (m); ¹³C NMR (126 MHz, Chloroform-d) δ: 159.6, 159.4 (d, J=252.3 Hz), 152.1 (d, J=257.0 Hz), 134.9, 130.3 (d, J=8.6 Hz), 129.5, 127.3 (dd, J=9.1, 2.3 Hz), 124.3 (d, J=3.6 Hz), 122.0 (d, J=7.7 Hz), 121.0 (dd, J=29.7, 10.7 Hz), 116.3 (dd, J=22.7, 2.7 Hz), 114.4 (d, J=9.1 Hz), 113.6 (d, J=2.3 Hz), 111.5 (dd, J=13.6, 8.6 Hz), 55.3. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0854.

  (Z)-(4-(1-Fluoro-2-(3-methoxyphenyl)vinyl)phenyl)- (methyl)sulfane (Z-12): Z-12 was prepared (84% yield as a white solid) according to the known method.^[18c] m.p. 108~114 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 7.55 (d, J=8.7 Hz, 1H), 7.49 (d, J=8.7 Hz, 1H), 7.33~7.29 (m, 1H), 7.29~7.26 (m, 1H), 7.25 (d, J=1.2 Hz, 1H), 7.23~7.16 (m, 2H), 6.82 (ddd, J=8.2, 2.6, 1.1 Hz, 1H), 6.24 (d, J=39.4 Hz, 1H), 3.84 (s, 3H), 2.51 (d, J=1.1 Hz, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -113.69 (d, J=38.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 159.7, 157.1 (d, J=258.1 Hz), 140.1, 137.4 (d, J=20.9 Hz), 135.0, 129.5, 127.1 (d, J=15.4 Hz), 126.1 (d, J=2.3 Hz), 124.7 (d, J=7.7 Hz), 121.6 (d, J=7.3 Hz), 113.6 (d, J=110.8 Hz), 105.2 (d, J=10.0 Hz), 55.2, 15.7 (d, J=64.0 Hz). HRMS (EI) calcd for C₁₆H₁₅OFS 274.0822, found 274.0825.

  (Z)-1-Fluoro-2-(1-fluoro-2-(3-methoxyphenyl)vinyl)- benzene (Z-13):Z-13 was prepared (43% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (500 MHz, Chloroform-d) δ: 7.64 (tt, J=7.8, 1.8 Hz, 1H), 7.35~7.24 (m, 2H), 7.24~7.19 (m, 3H), 7.17~7.10 (m, 1H), 6.88~6.82 (m, 1H), 6.50 (d, J=41.2 Hz, 1H), 3.84 (d, J=1.7 Hz, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -109.58 (dd, J=41.2, 9.1 Hz), -110.70~-113.39 (m); ¹³C NMR (126 MHz, Chloroform-d) δ: 159.6, 159.4 (d, J=252.3 Hz), 152.1 (d, J=257.0 Hz), 134.9, 130.3 (d, J=8.6 Hz), 129.5, 127.3 (dd, J=9.1, 2.3 Hz), 124.3 (d, J=3.6 Hz), 122.0 (d, J=7.7 Hz), 121.0 (dd, J=29.7, 10.7 Hz), 116.3 (dd, J=22.7, 2.7 Hz), 114.4 (d, J=9.1 Hz), 113.6 (d, J=2.3 Hz), 111.5 (dd, J=13.6, 8.6 Hz), 55.3. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0852.

  (Z)-1-(2-Fluoro-2-(4-fluorophenyl)vinyl)-2-methoxybenzene (Z-14):Z-14 was prepared (36% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.93 (dd, J=7.8, 1.7 Hz, 1H), 7.69~7.60 (m, 2H), 7.26 (s, 1H), 7.10 (t, J=8.8 Hz, 2H), 7.01 (t, J=7.6 Hz, 1H), 6.91 (d, J=7.1 Hz, 1H), 6.72 (d, J=40.7 Hz, 1H), 3.88 (s, 3H). ¹⁹F NMR (471 MHz, Chloroform-d) δ: -111.83~-112.93 (m), -115.31 (d, J=40.7 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 163.0 (d, J=249.4 Hz), 156.4, 156.4 (d, J=257.2 Hz), 129.9 (d, J=13.9 Hz), 128.5, 126.3 (t, J=7.7 Hz), 122.4 (d, J=3.7 Hz), 120.8, 115.6 (d, J=22.0 Hz), 110.5, 99.2 (d, J=8.1 Hz), 55.6. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0848.

  (Z)-1-(2-Fluoro-2-(4-methoxyphenyl)vinyl)-2-methoxy- benzene (Z-15):Z-15 was prepared (78% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.99~7.88 (m, 1H), 7.66 (dd, J=9.1, 5.3 Hz, 2H), 7.32~7.17 (m, 1H), 7.10 (t, J=8.8 Hz, 2H), 7.02 (t, J=7.6 Hz, 1H), 6.92 (d, J=9.3 Hz, 1H), 6.82~6.65 (m, 1H), 3.89 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -115.05 (d, J=41.6 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 160.1, 157.3 (d, J=257.1 Hz), 156.3, 129.8 (d, J=14.1 Hz), 128.1 (d, J=2.3 Hz), 127.7, 126.1, 125.9 (d, J=7.7 Hz), 122.8 (d, J=3.2 Hz), 120.7, 114.2, 113.9 (d, J=2.3 Hz), 110.5, 97.6 (d, J=8.6 Hz), 55.6, 55.4. HRMS (EI) calcd for C₁₆H₁₅O₂F 258.1051, found 258.1052.

  (Z)-1-(4-(1-Fluoro-2-(2-methoxyphenyl)vinyl)phenyl)- ethan-1-one (Z-16):Z-16 was prepared (57% yield as a white solid) according to the known method.^[18c] m.p. 93~96 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 8.03~7.92 (m, 2H), 7.75 (dd, J=8.6, 2.2 Hz, 2H), 7.32~7.25 (m, 3H), 7.05~6.97 (m, 1H), 6.95~6.87 (m, 1H), 3.89 (d, J=2.4 Hz, 3H), 2.62 (d, J=2.3 Hz, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ -116.97 (d, J=40.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 197.4, 156.7, 156.0 (d, J=257.5 Hz), 137.6 (d, J=28.2 Hz), 136.7, 130.1 (d, J=14.1 Hz), 129.2 (d, J=2.3 Hz), 128.6 (d, J=2.3 Hz), 124.2 (d, J=7.3 Hz), 121.9 (d, J=3.6 Hz), 120.8, 110.5, 101.9 (d, J=8.2 Hz), 55.6, 26.6. HRMS (EI) calcd for C₁₇H₁₅O₂F 270.1051, found 270.1052.

  Methyl (Z)-4-(1-fluoro-2-(2-methoxyphenyl)vinyl)ben- zoate (Z-17):Z-17 was prepared (58% yield as a white solid) according to the known method.^[18c] m.p. 70~75 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 8.06 (d, J=8.4 Hz, 2H), 7.99~7.92 (m, 1H), 7.73 (d, J=8.6 Hz, 2H), 7.29 (d, J=7.9 Hz, 1H), 7.05~6.83 (m, 3H), 3.94 (s, 3H), 3.89 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -116.91 (d, J=39.9 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 166.6, 156.7, 156.1 (d, J=257.5 Hz), 137.5 (d, J=28.2 Hz), 130.1 (d, J=14.5 Hz), 129.9, 129.8 (d, J=2.3 Hz), 129.1 (d, J=2.3 Hz), 124.0 (d, J=7.7 Hz), 122.0 (d, J=3.6 Hz), 120.8, 110.5, 101.7 (d, J=8.6 Hz), 55.6, 52.2. HRMS (EI) calcd for C₁₇H₁₅O₃F 286.1000, found 286.1002.

  (Z)-1-(2-Fluoro-2-(3-(trifluoromethyl)phenyl)vinyl)-2-methoxybenzene (Z-18):Z-18 was prepared (47% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.96 (dd, J=7.8, 1.8 Hz, 1H), 7.92 (s, 1H), 7.85 (d, J=7.9 Hz, 1H), 7.60 (d, J=7.4 Hz, 1H), 7.53 (t, J=7.7 Hz, 1H), 7.32~7.26 (m, 1H), 7.03 (t, J=7.6 Hz, 1H), 6.95~6.83 (m, 2H), 3.90 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -62.78, -116.90 (d, J=40.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 156.6, 155.6 (d, J=257.4 Hz), 134.2 (d, J=29.1 Hz), 131.7~130.5 (m), 130.1 (d, J=14.1 Hz), 129.1 (d, J=2.3 Hz), 127.4 (d, J=7.3 Hz), 125.2 (q, J=3.9 Hz), 124.0 (d, J=272.3 Hz), 121.8 (d, J=3.6 Hz), 121.1 (dd, J=7.7, 3.6 Hz), 120.8, 110.5, 100.9 (d, J=8.6 Hz), 80.8~72.1 (m), 55.6. HRMS (EI) calcd for C₁₆H₁₂OF₄ 296.0819, found 296.0820.

  (Z)-1-(2-Fluoro-2-(3-methoxyphenyl)vinyl)-2-methoxy- benzene (Z-19): Z-19 was prepared (54% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.95 (dd, J=7.8, 1.8 Hz, 1H), 7.37~7.18 (m, 4H), 7.01 (t, J=7.6 Hz, 1H), 6.94~6.89 (m, 2H), 6.80 (d, J=40.6 Hz, 1H), 3.88 (s, 3H), 3.87 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -115.42 (d, J=40.7 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 159.7 (d, J=2.2 Hz), 156.9 (d, J=257.9 Hz), 156.5, 134.8 (d, J=28.6 Hz), 130.0 (d, J=13.9 Hz), 129.6 (d, J=2.9 Hz), 128.6 (d, J=2.2 Hz), 122.4 (d, J=3.7 Hz), 120.7, 117.0 (d, J=7.3 Hz), 114.4, 110.5, 109.9 (d, J=8.1 Hz), 99.7 (d, J=8.8 Hz), 55.6, 55.4. HRMS (EI) calcd for C₁₆H₁₅O₂F 258.1050, found 258.1055.

  (Z)-1-(1-Fluoro-2-(2-methoxyphenyl)vinyl)-3, 5-bis(tri- fluoromethyl)benzene (Z-20): Z-20 was prepared (52% yield as a white solid) according to the known method.^[18c] m.p. 80~85 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 8.07 (s, 2H), 7.94 (dd, J=7.9, 1.9 Hz, 1H), 7.83 (s, 1H), 7.32 (td, J=7.9, 2.0 Hz, 1H), 7.07~6.87 (m, 3H), 3.92 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -63.01, -117.70 (d, J=39.9 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 156.8, 154.1 (d, J=256.8 Hz), 135.5 (d, J=30.1 Hz), 132.1 (q, J=33.0 Hz), 130.2 (d, J=13.9 Hz), 129.7, 124.2~123.7 (m), 123.2 (q, J=271.2 Hz), 122.0~121.9 (m), 121.2 (d, J=3.7 Hz), 120.8, 110.5, 102.7 (d, J=8.1 Hz), 55.6. HRMS (EI) calcd for C₁₇H₁₁OF₇ 364.0693, found 364.0694.

  (Z)-1-Fluoro-2-(1-fluoro-2-(2-methoxyphenyl)vinyl)benzene (Z-21): Z-21 was prepared (35% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.96 (dd, J=7.7, 1.8 Hz, 1H), 7.66 (td, J=7.8, 1.9 Hz, 1H), 7.36~7.27 (m, 2H), 7.24~7.11 (m, 2H), 7.06~6.87 (m, 3H), 3.88 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -109.18~-114.48 (m); ¹³C NMR (101 MHz, Chloroform-d) δ: 159.4 (dd, J=252.7, 5.5 Hz), 156.6, 152.0 (dd, J=256.0, 5.1 Hz), 130.2 (dd, J=11.7, 2.9 Hz), 130.0 (dd, J=7.0, 2.6 Hz), 128.8 (d, J=1.5 Hz), 127.4 (dd, J=7.7, 3.3 Hz), 124.2, 122.4 (d, J=2.9 Hz), 121.8~121.2 (m), 120.7, 116.7~115.8 (m), 110.5, 105.2 (dd, J=13.2, 8.1 Hz), 55.7. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0852.

  (Z)-1-(1-Fluoro-2-(2-methoxyphenyl)vinyl)-2-methyl- benzene (Z-22):Z-22 was prepared (52% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 8.01~7.94 (m, 1H), 7.51 (d, J=7.8 Hz, 1H), 7.33~7.25 (m, 1H), 7.24 (m, 2H), 7.07~6.99 (m, 1H), 6.95~6.88 (m, 1H), 6.58~6.22 (m, 1H), 3.86 (s, 3H), 2.50 (d, J=3.5 Hz, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -99.15 (dd, J=39.4, 3.9 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 158.7 (d, J=262.6 Hz), 156.4, 136.7, 133.7 (d, J=25.7 Hz), 130.8, 129.8 (d, J=13.6 Hz), 129.2, 128.9 (d, J=5.1 Hz), 128.4 (d, J=2.2 Hz), 125.7, 122.7 (d, J=4.0 Hz), 120.7, 110.6, 103.5 (d, J=9.2 Hz), 55.6, 20.8 (d, J=4.0 Hz). HRMS (EI) calcd for C₁₆H₁₅OF 242.1101, found 242.1103.

  Methyl (Z)-2-(1-fluoro-2-(2-methoxyphenyl)vinyl)ben- zoate (Z-23):Z-23 was prepared (29% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (400 MHz, Chloroform-d) δ: 7.96 (dd, J=7.8, 1.8 Hz, 1H), 7.81 (dd, J=7.6, 1.5 Hz, 1H), 7.63 (dt, J=7.7, 1.5 Hz, 1H), 7.57~7.52 (m, 1H), 7.49~7.43 (m, 1H), 7.32~7.24 (m, 1H), 7.02 (t, J=7.6 Hz, 1H), 6.93 (dd, J=8.3, 1.1 Hz, 1H), 6.54 (d, J=39.0 Hz, 1H), 3.93 (s, 3H), 3.88 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -99.92 (d, J=39.0 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 168.5, 157.4 (d, J=261.5 Hz), 156.4, 133.8 (d, J=26.3 Hz), 131.3, 130.4, 129.9 (d, J=13.6 Hz), 129.7, 129.5 (d, J=4.5 Hz), 129.1, 128.7 (d, J=2.3 Hz), 122.4 (d, J=4.1 Hz), 120.7, 110.5, 102.8 (d, J=8.2 Hz), 55.5, 52.6. HRMS (EI) calcd for C₁₇H₁₅O₃F 286.1000, found 242.1001.

  (Z)-(4-(2-(2, 6-Dichlorophenyl)-1-fluorovinyl)phenyl)- (methyl)sulfane (Z-24):Z-24 was prepared (58% yield as a white solid) according to the known method.^[18c] m.p. 113~120 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 7.63 (dt, J=5.0, 2.4 Hz, 2H), 7.38 (dd, J=5.4, 2.7 Hz, 2H), 7.34~7.27 (m, 2H), 7.20 (q, J=3.2 Hz, 1H), 6.43~6.26 (m, 1H), 2.54 (s, 3H), 1.58 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -106.69 (dd, J=37.3, 4.3 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 157.8 (d, J=258.2 Hz), 141.1, 135.5, 131.2, 128.9, 128.2 (d, J=27.9 Hz), 127.9, 126.1, 125.3 (d, J=6.6 Hz), 100.0 (d, J=15.4 Hz), 15.4. HRMS (EI) calcd for C₁₅H₁₁SFCl₂: 311.9937, found 311.9936.

  (Z)-2-(1-Fluoro-2-(2-methoxyphenyl)vinyl)thiophene (Z-25):Z-25 was prepared (61% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (500 MHz, Chloroform-d) δ:7.88 (d, J=7.8 Hz, 1H), 7.44~7.10 (m, 3H), 7.03 (d, J=4.0 Hz, 1H), 7.00~6.92 (m, 1H), 6.88 (dd, J=8.3, 2.7 Hz, 1H), 6.62 (dd, J=40.2, 2.4 Hz, 1H), 3.86 (d, J=3.4 Hz, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -109.02 (d, J=39.8 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 156.3, 153.0 (d, J=254.6 Hz), 136.9 (d, J=34.5 Hz), 129.8 (d, J=13.9 Hz), 128.5 (d, J=2.2 Hz), 127.7, 125.7, 124.5 (d, J=4.4 Hz), 122.2 (d, J=4.4 Hz), 120.8, 110.5, 99.0 (d, J=8.1 Hz), 55.6. HRMS (EI): calcd for C₁₃H₁₁SOF: 234.0509, found 234.0510.

  (Z)-3-(1-Fluoro-2-(4-methoxyphenyl)vinyl)pyridine (Z- 26):Z-26 was prepared (87% yield as a pale yellow oil) according to the known method.^{[18c] 1}H NMR (500 MHz, Chloroform-d) δ: 8.90 (s, 1H), 8.54 (d, J=5.5 Hz, 1H), 7.90 (t, J=6.9 Hz, 2H), 7.30 (d, J=7.2 Hz, 1H), 7.24 (d, J=8.2 Hz, 1H), 6.98 (t, J=7.7 Hz, 1H), 6.91~6.74 (m, 2H), 3.85 (d, J=1.8 Hz, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -118.11 (d, J=40.1 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 156.6, 154.6 (d, J=257.5 Hz), 149.4, 145.8 (d, J=8.1 Hz), 131.5 (d, J=6.6 Hz), 130.1 (d, J=13.9 Hz), 129.1 (d, J=2.2 Hz), 123.3 (d, J=2.9 Hz), 120.8, 110.5, 101.2 (d, J=8.1 Hz), 55.6. HRMS (EI) calcd for C₁₄H₁₂NOF 229.0897, found 229.0896.

  (Z)-2-(2-(4-Chlorophenyl)-1-fluorovinyl)-1-(pyrimidin- 2-yl)-1H-indole (Z-27):Z-27 was prepared (96% yield) according to the known method.^[20b] The data is consistent with the literature report.^[20b]

  4.3   General procedure for the synthesis of E-mono- fluorostilbenes

  To a 15 mL-quartz tube charged with a stirring bar was added the substrate Z-monofluorostilbenes (0.1 mmol, 1 equiv.), photocatalyst B (1.0 mg, 0.001 mmol, 1 mol%) and MeCN (2 mL) under air. The reaction vial was sealed with a rubber septum and then applying blue light to irradiate it. The mixture was stirred at room temperature until the reaction reached equilibrium (about 10 h). After the reaction was finished, the mixture was evaporated under vacuum to remove the solvent. The residue was purified by flash column chromatography on silica gel to afford a mixture of desired products with E- and Z-isomers (E:Z ratio was determined by ¹H NMR spectroscopy analysis).

  (E)-1-Fluoro-4-(1-fluoro-2-(4-methoxyphenyl)vinyl)- benzene (E-1): The total yield is 94% (23.1 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 82:18. ¹H NMR (500 MHz, Chloroform-d) δ: 7.49~7.36 (m, 2H), 7.10~7.02 (m, 2H), 7.03~6.93 (m, 2H), 6.83~6.73 (m, 2H), 6.40 (dd, J=21.5, 1.7 Hz, 1H), 3.79 (d, J=2.3 Hz, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -97.81 (d, J=21.1 Hz), -110.73; ¹³C NMR (101 MHz, Chloroform-d) δ: 163.0 (d, J=249.4 Hz), 158.8, 156.1 (d, J=244.3 Hz), 130.3 (dd, J=8.1, 5.1 Hz), 129.9 (d, J=2.9 Hz), 128.2 (d, J=30.1 Hz), 125.8 (d, J=12.5 Hz), 115.4 (d, J=21.3 Hz), 114.0, 108.8 (d, J=31.5 Hz), 55.2. HRMS (EI) calcd for C₁₅H₁₂OF₂: 246.0851, found 246.0848.

  (E)-1-(2-Fluoro-2-phenylvinyl)-4-methoxybenzene (E-2): The total yield is 92% (21.0 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 82:18. ¹H NMR (400 MHz, Chloroform-d) δ: 7.48~7.43 (m, 2H), 7.36~7.29 (m, 3H), 7.14~7.07 (m, 2H), 6.77 (d, J=8.8 Hz, 2H), 6.42 (d, J=21.8 Hz, 1H), 3.79 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -97.99 (d, J=21.8 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 158.7, 157.0 (d, J=244.3 Hz), 132.1 (d, J=28.6 Hz), 130.0 (d, J=2.9 Hz), 129.3, 128.3, 128.2 (d, J=4.4 Hz), 126.0 (d, J=12.5 Hz), 113.9, 108.9 (d, J=30.8 Hz), 55.2. HRMS (EI) calcd for C₁₅H₁₃OF 228.0945, found 228.043.

  (E)-1-(2-Fluoro-2-(4-(trifluoromethyl)phenyl)vinyl)-4- methoxybenzene (E-3): The total yield is 90% (26.6 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 83:17. ¹H NMR (500 MHz, Chloroform-d) δ: 7.51 (s, 4H), 7.29~7.22 (m, 1H), 7.03 (d, J=8.0 Hz, 1H), 6.90 (d, J=8.4 Hz, 1H), 6.78 (t, J=7.6 Hz, 1H), 6.62 (d, J=22.0 Hz, 1H), 3.81 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -62.87, -100.47 (d, J=21.7 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 157.1 (d, J=2.7 Hz), 156.0 (d, J=244.3 Hz), 135.6 (d, J=30.9 Hz), 130.9 (q, J=32.8 Hz), 130.1 (d, J=1.8 Hz), 129.3, 128.0 (d, J=5.9 Hz), 125.1 (q, J=3.9 Hz), 124.4 (d, J=7.3 Hz), 123.9 (d, J=272.3 Hz), 122.0 (d, J=11.8 Hz), 120.6, 110.8, 107.1 (d, J=31.8 Hz), 101.6 (d, J=8.2 Hz), 55.4. HRMS (EI) calcd for C₁₆H₁₂OF₄: 296.0819, found 296.0813.

  (E)-4, 4'-(1-Fluoroethene-1, 2-diyl)bis(methoxybenzene) (E-4): The total yield is 93% (24.0 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 78:22. ¹H NMR (400 MHz, Chloroform-d) δ: 7.41~7.31 (m, 2H), 7.15~7.04 (m, 2H), 6.87~6.68 (m, 4H), 6.32 (d, J=21.5 Hz, 1H), 3.80 (dd, J=12.8, 1.9 Hz, 6H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -96.93 (d, J=21.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 160.2, 158.5, 157.0 (d, J=243.9 Hz), 130.2~129.4 (m), 126.4 (d, J=12.7 Hz), 124.5 (d, J=30.0 Hz), 113.8 (d, J=23.6 Hz), 107.5 (d, J=31.8 Hz), 55.2 (d, J=6.8 Hz). HRMS (EI) calcd for C₁₆H₁₅O₂F 258.1051, found 258.1050.

  (E)-1-(2-Fluoro-2-phenylvinyl)-4-(trifluoromethyl)ben- zene (E-5): The total yield is 96% (25.5 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 77:23. ¹H NMR (400 MHz, Chloroform-d) δ: 7.45 (d, J=8.4 Hz, 2H), 7.41 (dd, J=7.5, 1.4 Hz, 2H), 7.33 (q, J=6.6 Hz, 3H), 7.24 (d, J=8.3 Hz, 2H), 6.44 (d, J=20.7 Hz, 1H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -62.62, -91.56; ¹³C NMR (101 MHz, Chloroform-d) δ: 159.4 (d, J=250.2 Hz), 137.7 (d, J=12.5 Hz), 131.3 (d, J=28.6 Hz), 130.1, 129.0 (d, J=2.9 Hz), 128.6, 128.4 (d, J=4.4 Hz), 125.4 (t, J=5.5 Hz), 124.1 (q, J=273.2 Hz), 108.2 (d, J=32.3 Hz). HRMS (EI) calcd for C₁₅H₁₀F₄ 266.0713, found 266.0710.

  (E)-1-Chloro-3-(1-fluoro-2-(4-methoxyphenyl)vinyl)- benzene (E-6): The total yield is 91% (23.8 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 78:22. ¹H NMR (400 MHz, Chloroform-d) δ: 7.45 (t, J=2.0 Hz, 1H), 7.29 (dt, J=5.4, 2.5 Hz, 2H), 7.22 (d, J=8.3 Hz, 1H), 7.09 (d, J=8.8 Hz, 2H), 6.79 (d, J=8.8 Hz, 2H), 6.45 (d, J=21.6 Hz, 1H), 3.79 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -99.65 (d, J=21.6 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 158.9, 155.4 (d, J=244.3 Hz), 134.3, 133.8 (d, J=29.5 Hz), 130.0 (d, J=2.7 Hz), 129.5 (d, J=17.3 Hz), 128.0 (d, J=5.0 Hz), 126.4 (d, J=5.0 Hz), 125.4 (d, J=12.3 Hz), 114.1, 110.0 (d, J=30.4 Hz), 55.3. HRMS (EI) calcd for C₁₅H₁₂OFCl 262.0555, found 262.0557.

  (E)-1-(1-Fluoro-2-(4-methoxyphenyl)vinyl)-3-(trifluo- romethyl)benzene (E-7): The total yield is 89% (26.3 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 83:17. ¹H NMR (500 MHz, Chloroform-d) δ: 7.66 (s, 1H), 7.53 (dd, J=11.9, 7.3 Hz, 2H), 7.34 (t, J=7.9 Hz, 1H), 7.23 (t, J=7.8 Hz, 1H), 7.01 (dd, J=7.6, 1.7 Hz, 1H), 6.87 (d, J=8.4 Hz, 1H), 6.76 (t, J=7.5 Hz, 1H), 6.59 (d, J=21.8 Hz, 1H), 3.78 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -63.00, -100.60 (d, J=21.7 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 157.0 (d, J=2.7 Hz), 155.9 (d, J=244.3 Hz), 133.0 (d, J=30.0 Hz), 130.9 (d, J=6.4 Hz), 130.0 (d, J=2.3 Hz), 129.3, 129.1 (d, J=2.3 Hz), 128.5, 125.7 (q, J=3.6 Hz), 124.5 (dd, J=5.9, 4.1 Hz), 123.8 (d, J=272.4 Hz), 121.9 (d, J=12.3 Hz), 120.5, 110.8, 106.6 (d, J=31.8 Hz), 55.4. HRMS (EI) calcd for C₁₆H₁₂OF₄: 296.0819, found 296.0812.

  (E)-1-Chloro-4-(1-fluoro-2-(4-(trifluoromethyl)phenyl)- vinyl)-2-methylbenzene (E-8): The total yield is 90% (28.3 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 85:15. ¹H NMR (400 MHz, Chloroform-d) δ: 7.48 (d, J=8.3 Hz, 2H), 7.31~7.21 (m, 4H), 7.12 (dd, J=8.3, 2.5 Hz, 1H), 6.44 (d, J=20.5 Hz, 1H), 2.33 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -62.65, -92.24 (d, J=20.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 158.4 (d, J=250.2 Hz), 137.5 (d, J=12.7 Hz), 136.6, 136.2 (d, J=2.3 Hz), 130.6 (d, J=4.5 Hz), 129.7 (d, J=28.6 Hz), 129.3, 129.0 (d, J=2.7 Hz), 127.2 (d, J=5.0 Hz), 125.4 (q, J=3.9 Hz), 124.0 (q, J=272.0 Hz), 108.5 (d, J=31.8 Hz), 20.0. HRMS (EI) calcd for C₁₆H₁₁F₄Cl 314.0480, found 314.0481.

  (E)-1-(1-Fluoro-2-(4-methoxyphenyl)vinyl)-2-methyl- benzene (E-9): The total yield is 88% (21.3 mg as a pale yellow oil) after column chromatography (eluent: petro- leum ether).The ratio of E:Z is 83:17. ¹H NMR (500 MHz, Chloroform-d) δ: 7.34~7.12 (m, 3H), 7.09 (d, J=8.1 Hz, 2H), 6.80 (dd, J=8.4, 3.2 Hz, 1H), 6.70 (dd, J=20.6, 4.0 Hz, 1H), 6.61 (ddd, J=24.3, 7.6, 2.6 Hz, 2H), 3.80 (s, 3H), 2.26 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -86.83 (d, J=19.9 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 158.4 (d, J=249.8 Hz), 156.7 (d, J=3.6 Hz), 137.6, 132.1 (d, J=26.3 Hz), 130.5, 130.2 (d, J=2.7 Hz), 129.6 (d, J=2.7 Hz), 128.8, 128.2, 125.9, 122.5 (d, J=11.8 Hz), 120.2, 110.5, 105.7 (d, J=32.7 Hz), 55.5, 19.6. HRMS (EI) calcd for C₁₆H₁₅OF: 242.1101, found 242.1103.

  (E)-1-(1-Fluoro-2-(4-methoxyphenyl)vinyl)-2, 4-dimethylbenzene (E-10): The total yield is 92% (23.6 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 82:18. ¹H NMR (500 MHz, Chloroform-d) δ: 7.21 (d, J=3.2 Hz, 1H), 7.18~7.10 (m, 1H), 7.07 (d, J=3.1 Hz, 1H), 7.00 (d, J=3.2 Hz, 1H), 6.91 (s, 1H), 6.80~6.76 (m, 1H), 6.70~6.54 (m, 2H), 3.79 (d, J=3.2 Hz, 3H), 2.24 (d, J=44.3 Hz, 6H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -85.83 (d, J=20.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 158.6 (d, J=249.8 Hz), 156.7 (d, J=3.6 Hz), 139.6 (d, J=2.7 Hz), 137.4, 131.3, 130.1 (d, J=2.7 Hz), 129.2 (d, J=26.8 Hz), 128.7, 128.0, 126.6, 122.7 (d, J=11.8 Hz), 120.2, 110.4, 105.3 (d, J=33.6 Hz), 55.5, 21.3, 19.5. HRMS (EI) calcd for C₁₇H₁₇OF: 256.1258, found 256.1256.

  (E)-1-(2-Fluoro-2-(4-fluorophenyl)vinyl)-3-methoxy- benzene (E-11): The total yield is 91% (22.4 mg as a pale yellow oil) after column chromatography (eluent: petro- leum ether). The ratio of E:Z is 83:17. ¹H NMR (400 MHz, Chloroform-d) δ: 7.44 (dd, J=9.2, 5.3 Hz, 2H), 7.16 (t, J=7.9 Hz, 1H), 7.07~6.92 (m, 2H), 6.79~6.72 (m, 2H), 6.70 (s, 1H), 6.44 (d, J=21.3 Hz, 1H), 3.70 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -95.46 (d, J=21.1 Hz), -110.28 (d, J=4.8 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 163.2 (d, J=248.7 Hz), 159.6, 157.1 (d, J=246.5 Hz), 134.9 (d, J=12.5 Hz), 130.4 (dd, J=8.4, 4.8 Hz), 129.6, 128.0 (dd, J=30.1, 3.7 Hz), 121.4 (d, J=2.9 Hz), 115.5 (d, J=22.0 Hz), 114.1 (d, J=2.9 Hz), 113.0, 109.2 (d, J=30.8 Hz), 55.1. HRMS (EI) calcd for C₁₅H₁₂- OF₂ 246.0851, found 246.0850.

  (E)-(4-(1-Fluoro-2-(3-methoxyphenyl)vinyl)phenyl)- (methyl)sulfane (E-12): The total yield is 89% (24.4 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 81:19. ¹H NMR (500 MHz, Chloroform-d) δ: 7.35 (d, J=8.7 Hz, 2H), 7.14 (dt, J=7.9, 3.5 Hz, 3H), 6.81~6.69 (m, 3H), 6.39 (d, J=21.5 Hz, 1H), 3.70 (s, 3H), 2.48 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -96.71 (d, J=21.8 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 159.6, 157.7 (d, J=245.8 Hz), 140.8, 135.2 (d, J=12.5 Hz), 129.5, 128.6 (d, J=5.1 Hz), 128.2 (d, J=29.3 Hz), 127.1 (d, J=10.3 Hz), 125.5, 121.4 (d, J=2.9 Hz), 114.1 (d, J=2.9 Hz), 112.9, 108.9 (d, J=32.3 Hz), 55.1, 15.2. HRMS (EI) calcd for C₁₆H₁₅OFS 274.0822, found 274.0820.

  (E)-1-Fluoro-2-(1-fluoro-2-(3-methoxyphenyl)vinyl)- benzene (E-13): The total yield is 88% (21.6 mg as a pale yellow oil) after column chromatography (eluent: petro- leum ether). The ratio of E:Z is 91:9. ¹H NMR (500 MHz, Chloroform-d) δ: 7.42 (td, J=7.3, 6.5, 3.7 Hz, 2H), 7.18~7.06 (m, 3H), 6.73 (dd, J=8.3, 2.5 Hz, 1H), 6.65 (d, J=7.8 Hz, 1H), 6.57 (t, J=10.0 Hz, 2H), 3.62 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -91.59 (dd, J=19.9, 8.7 Hz), -109.35~-113.11 (m); ¹³C NMR (101 MHz, Chloroform-d) δ: 160.2 (d, J=253.0 Hz), 159.4, 153.3 (d, J=248.6 Hz), 134.4 (d, J=11.7 Hz), 131.9 (dd, J=8.1, 2.2 Hz), 131.4, 129.3, 124.3 (d, J=4.4 Hz), 120.9 (d, J=3.7 Hz), 120.4 (dd, J=28.6, 14.7 Hz), 116.3 (d, J=21.3 Hz), 113.2, 112.4 (d, J=30.1 Hz), 55.0. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0850.

  (E)-1-(2-Fluoro-2-(4-fluorophenyl)vinyl)-2-methoxybenzene (E-14): The total yield is 91% (22.4 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 86:14. ¹H NMR (500 MHz, Chloroform-d) δ: 7.46~7.39 (m, 2H), 7.15 (td, J=8.1, 2.2 Hz, 1H), 7.00 (td, J=8.9, 2.4 Hz, 2H), 6.75 (t, J=8.1 Hz, 2H), 6.69 (s, 1H), 6.43 (dd, J=21.4, 2.3 Hz, 1H), 3.73~3.63 (m, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -97.27 (d, J=21.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 163.2 (d, J=250.9 Hz), 159.6, 156.1, 134.9 (d, J=12.7 Hz), 130.4 (dd, J=8.6, 5.0 Hz), 129.6, 128.0 (d, J=26.3 Hz), 121.3 (d, J=3.2 Hz), 115.5 (d, J=22.3 Hz), 114.1 (d, J=2.7 Hz), 113.0, 109.2 (d, J=31.3 Hz), 55.1. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0850.

  (E)-1-(2-Fluoro-2-(4-methoxyphenyl)vinyl)-2-methoxy- benzene (E-15): The total yield is 84% (21.7 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 83:17. ¹H NMR (500 MHz, Chloroform-d) δ: 7.35 (d, J=8.7 Hz, 2H), 7.19 (ddd, J=8.9, 7.6, 1.9 Hz, 1H), 7.07 (dd, J=7.6, 2.3 Hz, 1H), 6.87 (d, J=8.1 Hz, 1H), 6.81~6.77 (m, 2H), 6.74 (dd, J=7.6, 1.1 Hz, 1H), 6.43 (d, J=21.8 Hz, 1H), 3.83 (s, 3H), 3.79 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -96.64 (d, J=21.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 160.2, 157.7 (d, J=244.3 Hz), 157.0 (d, J=2.7 Hz), 130.1, 129.4 (d, J=5.4 Hz), 128.4, 124.6 (d, J=30.0 Hz), 123.0 (d, J=12.7 Hz), 120.4, 113.5, 110.7, 103.4 (d, J=33.6 Hz), 55.4 (d, J=30.0 Hz). HRMS (EI) calcd for C₁₆H₁₅O₂F 258.1051, found 258.1052.

  (E)-1-(4-(1-Fluoro-2-(2-methoxyphenyl)vinyl)phenyl)ethan-1-one (E-16): The total yield is 93% (25.1 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 79:21. ¹H NMR (400 MHz, Chloroform-d) δ: 7.88~7.78 (m, 2H), 7.50 (d, =8.3 Hz, 2H), 7.25~7.21 (m, 1H), 7.04 (ddd, J=7.6, 1.8, 0.9 Hz, 1H), 6.89 (d, J=8.1 Hz, 1H), 6.76 (td, J=7.5, 1.3 Hz, 1H), 6.63 (d, J=21.8 Hz, 1H), 3.81 (s, 3H), 2.57 (s, 3H). ¹⁹F NMR (376 MHz, Chloroform-d) δ: -100.46 (d, J=21.8 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 197.5, 157.1 (d, J=2.9 Hz), 156.3 (d, J=244.2 Hz), 137.1, 136.6 (d, J=28.6 Hz), 130.2 (d, J=2.2 Hz), 129.2, 128.1, 127.9 (d, J=5.9 Hz), 122.1 (d, J=11.7 Hz), 120.5, 110.7, 107.3 (d, J=32.3 Hz), 55.4, 26.6. HRMS (EI) calcd for C₁₇H₁₅- O₂F: 270.1051, found 270.1050.

  Methyl (E)-4-(1-fluoro-2-(2-methoxyphenyl)vinyl)ben- zoate (E-17): The total yield is 92% (26.3 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 82:18. ¹H NMR (400 MHz, Chloroform-d) δ: 7.96~7.87 (m, 2H), 7.48 (d, J=8.4 Hz, 2H), 7.26~7.19 (m, 1H), 7.03 (dt, J=7.6, 1.7 Hz, 1H), 6.89 (d, J=7.9 Hz, 1H), 6.76 (td, J=7.5, 1.3 Hz, 1H), 6.62 (d, J=21.8 Hz, 1H), 3.90 (s, 3H), 3.81 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -100.24; ¹³C NMR (126 MHz, Chloroform-d) δ: 166.5, 157.1 (d, J=2.7 Hz), 156.4 (d, J=244.4 Hz), 136.5 (d, J=29.1 Hz), 130.4, 130.2 (d, J=1.8 Hz), 129.3, 129.2, 127.7 (d, J=5.4 Hz), 122.1 (d, J=11.8 Hz), 120.5, 110.7, 107.0 (d, J=32.2 Hz), 55.4, 52.2. HRMS (EI) calcd for C₁₇H₁₅O₃F: 286.1000, found 286.0996.

  (E)-1-(2-Fluoro-2-(3-(trifluoromethyl)phenyl)vinyl)-2- methoxybenzene (E-18): The total yield is 85% (25.2 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 86:14. ¹H NMR (400 MHz, Chloroform-d) δ: 7.69 (s, 1H), 7.56 (t, J=9.1 Hz, 2H), 7.40~7.33 (m, 1H), 7.29~7.21 (m, 1H), 7.04 (dt, J=7.6, 1.6 Hz, 1H), 6.90 (d, J=8.2 Hz, 1H), 6.78 (td, J=7.5, 1.2 Hz, 1H), 6.62 (d, J=21.8 Hz, 1H), 3.81 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -63.02, -100.60 (d, J=21.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 157.0 (d, J=2.7 Hz), 155.9 (d, J=243.9 Hz), 133.0 (d, J=30.0 Hz), 130.9 (d, J=5.9 Hz), 130.7 (d, J=32.7 Hz), 130.0 (d, J=2.3 Hz), 129.2, 128.5, 125.7 (d, J=4.1 Hz), 124.6, 122.7, 121.9 (d, J=12.3 Hz), 120.5, 110.8, 106.6 (d, J=31.8 Hz), 55.4. HRMS (EI) calcd for C₁₆H₁₂OF₄: 296.0819, found 296.0817.

  (E)-1-(2-Fluoro-2-(3-methoxyphenyl)vinyl)-2-methoxy- benzene (E-19): The total yield is 88% (22.7 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 85:15. ¹H NMR (400 MHz, Chloroform-d) δ: 7.24~7.14 (m, 2H), 7.09 (dt, J=7.6, 1.3 Hz, 1H), 7.01 (d, J=7.5 Hz, 1H), 6.96 (t, J=2.1 Hz, 1H), 6.92~6.83 (m, 2H), 6.77 (td, J=7.5, 1.2 Hz, 1H), 6.54 (d, J=21.9 Hz, 1H), 3.83 (s, 3H), 3.67 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -97.95 (d, J=21.8 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 159.2, 157.4 (d, J=245.1 Hz), 157.1, 133.3 (d, J=29.3 Hz), 130.2, 129.2, 128.7, 122.7 (d, J=12.5 Hz), 120.4, 120.3, 115.6, 112.7 (d, J=5.9 Hz), 110.6, 105.1 (d, J=32.3 Hz), 55.3 (d, J=33.7 Hz). HRMS (EI) calcd for C₁₆H₁₅O₂F 258.1051, found 258.1053.

  (E)-1-(1-Fluoro-2-(2-methoxyphenyl)vinyl)-3, 5-bis(tri- fluoromethyl)benzene (E-20): The total yield is 87% (31.7 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 82:18. ¹H NMR (500 MHz, Chloroform-d) δ: 7.82 (s, 2H), 7.77 (s, 1H), 7.33~7.27 (m, 1H), 7.04 (d, J=7.5 Hz, 1H), 6.92 (d, J=8.2 Hz, 1H), 6.82 (t, J=7.6 Hz, 1H), 6.71 (d, J=21.5 Hz, 1H), 3.78 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -63.27, -103.37 (d, J=21.7 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 156.9 (d, J=2.7 Hz), 154.2 (d, J=243.9 Hz), 134.3 (d, J=30.9 Hz), 131.5 (q, J=34.3 Hz), 129.9 (d, J=2.7 Hz), 127.5, 122.7 (q, J=272.8 Hz), 122.8~122.3 (m), 121.0 (d, J=11.8 Hz), 120.7, 111.0, 108.5 (d, J=30.9 Hz), 55.3. HRMS (EI) calcd for C₁₇H₁₁OF₇ 364.0693, found 364.0690.

  (E)-1-Fluoro-2-(1-fluoro-2-(2-methoxyphenyl)vinyl)- benzene (E-21): The total yield is 90% (22.1 mg as a pale yellow oil) after column chromatography (eluent: petro- leum ether). The ratio of E:Z is 88:12. ¹H NMR (500 MHz, Chloroform-d) δ: 7.36 (q, J=5.9, 4.8 Hz, 2H), 7.21~7.13 (m, 1H), 7.07 (dt, J=18.8, 8.5 Hz, 2H), 6.85 (dd, J=7.9, 5.3 Hz, 2H), 6.75 (d, J=19.5 Hz, 1H), 6.68 (t, J=7.6 Hz, 1H), 3.82 (d, J=1.5 Hz, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -93.51 (dd, J=20.8, 9.5 Hz), -111.09 (dd, J=10.0, 5.6 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 160.1 (d, J=251.6 Hz), 156.9 (d, J=3.2 Hz), 153.1 (d, J=246.6 Hz), 131.4 (d, J=8.6 Hz), 131.0 (d, J=2.7 Hz), 129.0, 128.7, 124.0 (d, J=3.6 Hz), 122.3 (d, J=11.8 Hz), 120.7 (dd, J=29.1, 14.9 Hz), 120.3, 116.2 (d, J=21.3 Hz), 110.5, 107.8 (d, J=31.3 Hz), 55.5. HRMS (EI) calcd for C₁₅H₁₂OF₂ 246.0851, found 246.0850.

  (E)-1-(1-Fluoro-2-(2-methoxyphenyl)vinyl)-2-methyl- benzene (E-22): The total yield is 85% (20.6 mg as a pale yellow oil) after column chromatography (eluent: petro- leum ether). The ratio of E:Z is 89:11. ¹H NMR (400 MHz, Chloroform-d) δ: 7.33~7.21 (m, 3H), 7.18~7.08 (m, 2H), 6.84 (d, J=8.2 Hz, 1H), 6.75 (d, J=20.7 Hz, 1H), 6.70~6.58 (m, 2H), 3.84 (s, 3H), 2.30 (d, J=2.7 Hz, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -86.79 (d, J=20.4 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 158.4 (d, J=249.6 Hz), 156.7 (d, J=3.2 Hz), 137.6, 132.1 (d, J=26.3 Hz), 130.5 (d, J=1.8 Hz), 130.2 (d, J=3.2 Hz), 129.6 (d, J=2.7 Hz), 128.8 (d, J=2.3 Hz), 128.1, 125.8, 122.5 (d, J=12.3 Hz), 120.2, 110.5, 105.7 (d, J=32.7 Hz), 55.5, 19.6. HRMS (EI) calcd for C₁₆H₁₅OF 242.1103, found 242.1101.

  Methyl (E)-2-(1-fluoro-2-(2-methoxyphenyl)vinyl)ben- zoate (E-23): The total yield is 94% (26.9 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 86:14. ¹H NMR (400 MHz, Chloroform-d) δ: 8.00~7.90 (m, 1H), 7.48~7.34 (m, 2H), 7.33~7.28 (m, 1H), 7.12 (ddd, J=8.6, 7.4, 1.7 Hz, 1H), 6.82 (d, J=7.3 Hz, 1H), 6.76 (dd, J=7.6, 2.4 Hz, 1H), 6.67 (d, J=20.1 Hz, 1H), 6.62 (td, J=7.5, 1.2 Hz, 1H), 3.89 (s, 3H), 3.83 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -87.97; ¹³C NMR (126 MHz, Chloroform-d) δ: 167.1, 157.8 (d, J=248.7 Hz), 156.9 (d, J=3.2 Hz), 133.0 (d, J=27.2 Hz), 131.9, 131.7 (d, J=3.2 Hz), 131.0, 130.5 (d, J=1.8 Hz), 129.9 (d, J=1.8 Hz), 129.5 (d, J=2.3 Hz), 128.3, 122.5 (d, J=11.4 Hz), 120.3, 110.4, 105.4 (d, J=30.9 Hz), 55.4, 52.4. HRMS (EI) calcd for C₁₇H₁₅O₃F 286.1000, found 286.0998.

  (E)-(4-(2-(2, 6-Dichlorophenyl)-1-fluorovinyl)phenyl)- (methyl)sulfane (E-24): The total yield is 78% (24.3 mg as pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 76:24. ¹H NMR (500 MHz, Chloroform-d) δ: 7.31 (d, J=8.1 Hz, 2H), 7.17 (t, J=8.1 Hz, 1H), 7.13 (d, J=8.5 Hz, 2H), 7.07 (d, J=8.5 Hz, 2H), 6.22 (d, J=19.2 Hz, 1H), 2.43 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -100.23 (d, J=19.9 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 159.1 (d, J=248.9 Hz), 141.0, 135.6 (d, J=2.7 Hz), 132.0 (d, J=14.1 Hz), 129.2, 128.2, 127.9, 126.8 (d, J=6.4 Hz), 125.4, 103.2 (d, J=36.8 Hz), 15.0. HRMS (EI) calcd for C₁₅H₁₁SFCl₂ 311.9937, found 311.9936.

  (E)-2-(1-Fluoro-2-(2-methoxyphenyl)vinyl)thiophene (E-25): The total yield is 95% (22.2 mg as pale yellow oil) after column chromatography (eluent: petroleum ether). The ratio of E:Z is 78:22. ¹H NMR (500 MHz, Chloroform-d) δ: 7.34~7.26 (m, 2H), 7.22 (s, 1H), 7.18 (s, 1H), 6.97~6.85 (m, 3H), 6.40 (dd, J=20.7, 3.1 Hz, 1H), 3.83 (s, 3H); ¹⁹F NMR (471 MHz, Chloroform-d) δ: -96.80 (d, J=20.8 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 157.4 (d, J=2.3 Hz), 152.9 (d, J=239.8 Hz), 133.7 (d, J=35.0 Hz), 130.8 (d, J=2.3 Hz), 129.4, 127.4 (d, J=5.4 Hz), 127.0, 126.6, 122.0 (d, J=12.7 Hz), 120.6, 110.8, 104.4 (d, J=31.8 Hz), 55.5. HRMS (EI) calcd for C₁₃H₁₁SOF 234.0509, found 234.0507.

  (E)-3-(1-Fluoro-2-(4-methoxyphenyl)vinyl)pyridine (E-26): The total yield is 95% (21.8 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether:ethyl acetate, V:V=10:1). The ratio of E:Z is 88:12. ¹H NMR (400 MHz, Chloroform-d) δ: 8.65~8.56 (m, 1H), 8.51 (dd, J=4.9, 1.7 Hz, 1H), 7.69 (d, J=7.9 Hz, 1H), 7.25~7.17 (m, 2H), 7.02 (dt, J=7.6, 1.5 Hz, 1H), 6.88 (d, J=8.3 Hz, 1H), 6.78 (td, J=7.5, 1.2 Hz, 1H), 6.62 (d, J=21.5 Hz, 1H), 3.80 (s, 3H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -101.86 (d, J=21.1 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 157.1 (d, J=2.9 Hz), 155.0 (d, J=245.0 Hz), 149.8, 148.9 (d, J=5.9 Hz), 134.9 (d, J=5.1 Hz), 130.0 (d, J=2.2 Hz), 129.3, 122.9, 120.7, 110.8, 107.1 (d, J=31.5 Hz), 55.4. HRMS (EI) calcd for C₁₄H₁₂NOF 229.0897, found 229.0896.

  (E)-2-(2-(4-Chlorophenyl)-1-fluorovinyl)-1-(pyrimidin-2-yl)-1H-indole (E-27): The total yield is 92% (32.2 mg as a pale yellow oil) after column chromatography (eluent: petroleum ether:ethyl acetate, V:V=20:1). The ratio of E:Z is 75:25. ¹H NMR (400 MHz, Chloroform-d) δ: 8.76 (d, J=4.8 Hz, 2H), 8.58~8.47 (m, 1H), 7.61~7.55 (m, 1H), 7.40 (ddt, J=8.4, 7.1, 1.2 Hz, 1H), 7.26 (s, 1H), 7.17~7.08 (m, 5H), 6.81 (dd, J=3.5, 0.9 Hz, 1H), 6.43 (d, J=18.0 Hz, 1H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -90.78 (d, J=4.1 Hz); ¹³C NMR (126 MHz, Chloroform-d) δ: 157.1, 156.3, 151.6 (d, J=246.6 Hz), 136.0 (d, J=1.8 Hz), 131.6, 131.5 (d, J=10.4 Hz), 129.2~128.4 (m), 128.6 (J=27.8 Hz), 127.5, 127.5 (d, J=8.3 Hz), 124.2, 121.5, 120.5, 116.3, 113.9, 111.7 (d, J=5.5 Hz), 109.2 (d, J=30.9 Hz). HRMS (EI) calcd for C₂₀H₁₃N₃ClF 349.0777, found 349.0774.

  (E)-5-(2-Fluoro-2-(4-methoxyphenyl)vinyl)-1, 2, 3-trimethoxybenzene (E-30): The total yield is 87% (27.7 mg as pale yellow oil) after column chromatography (eluent: petroleum ether:ethyl acetate, V:V=20:1). The ratio of E:Z is 71:29. ¹H NMR (400 MHz, Chloroform-d) δ: 7.41 (d, J=9.1 Hz, 2H), 6.85 (d, J=8.8 Hz, 2H), 6.39 (s, 2H), 6.29 (d, J=21.3 Hz, 1H), 3.82 (dd, J=5.6, 1.2 Hz, 6H), 3.68 (d, J=1.1 Hz, 6H); ¹⁹F NMR (376 MHz, Chloroform-d) δ: -95.08 (d, J=21.1 Hz); ¹³C NMR (101 MHz, Chloroform-d) δ: 160.5, 157.8 (d, J=246.5 Hz), 153.1, 137.0, 130.0 (d, J=4.4 Hz), 129.5 (d, J=13.2 Hz), 124.2 (d, J=29.3 Hz), 113.7, 108.1 (d, J=32.3 Hz), 105.8 (d, J=3.7 Hz), 60.9, 55.9, 55.3. HRMS (EI) calcd for C₁₈H₁₉O₄F 318.1262, found 318.1261.

  Acknowledgements  We also thank Prof. Ruibo Wu, Dr. Xiaowen Tang and Mr. Xiu-Cai Chen at Sun Yat-sen University for helpful discussions.

  Supporting Information  The experimental procedures for the preparation of Z-monofluorostilbenes and spectra of reported compounds is available free of charge via the Internet at http://sioc-journal.cn/

  
  Dedicated to Professor Henry N. C. Wong on the occasion of his 70th birthday.
  
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  Figure 1  Selected bioactive monofluoroalkenes

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  Scheme 1  Different approaches toward E-monofluorostilbenes and photocatalytic isomerization of alkenes

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  Scheme 2  Synthetic utility and plausible mechanism

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  Table 1.  Optimization of the reaction conditions^a

  Entry	Photocatalyst	ET/(kJ•mol-1)b	Solvent	E:Zc
  1d	Benzil	223.4	MeCN	47:53
  2d	Fluorenone	223.0	MeCN	59:41
  3d	(—)-Riboflavin	209.2	MeCN	18:82
  4	A	252.7	MeCN	76:24
  5	Ir(ppy)3	235.6	MeCN	78:22
  6	B	221.8	MeCN	82:18
  7	C	215.1	MeCN	71:29
  8	[Ru(bpy)3]Cl2	205.0	MeCN	75:25
  9	B	221.8	EtOAc	78:22
  10	B	221.8	EtOH	77:23
  11	B	221.8	THF	75:25
  12e	B	221.8	MeCN	80:20
  13f	B	221.8	MeCN	80:20
  14	—		MeCN	< 1:99
  15g	B	221.8	MeCN	< 1:99
  a General reaction conditions: 18 W blue LEDs, Z-1 (0.1 mmol, 1.0 equiv.), photocatalyst (0.001 mmol, 1 mol%), solvent (2.0 mL), air, r.t., 10 h. b ET: Triplet state energy. c Determined by 1H NMR spectroscopy of the crude product. d 5 mol% catalyst loading was employed. e 1 drop of water was added. f Conducted under argon atmosphere. g Performed in darkness.

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  Table 2.  Substrate scope of the photoisomerization reactions

  a Isolated yield. E:Z ratio was determined by 1H NMR spectroscopy analysis. b 5 mol% benzil was used instead of cat. B.

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