English

• 1.   Introduction

  Recently, substituted quinoline derivatives have aroused the interest and research concern of many researchers, mainly due to their fine biological activities and broad applications in medicinal chemistry.^[1] Among them, 3-substituted quinolones is one of the most important quinoline derivatives and can be found in anticancer, antidepressant, and anti-psychotic molecules.^[2] The synthesis of 3-substituted quinolines has been widely reported.^[3] N-Propargylaniline derivatives can be used for synthesizing many significant nitrogen-containing heterocyclic compounds, including 3-substituted quinolines.^[4] In recent years, visible light as a clean and renewable chemical energy has been widely utilized to promote various organic synthetic transformations.^[5] N-Propargylamines have been proven to be efficient radical acceptors under visible light irradiation. In 2018, Zhang et al.^[4b] developed an efficient eosin Y-catalyzed three component sulfonylation of N-propargylanilines with DABSO (1, 4-diazabicyclo- [2.2.2]octane bis(sulfur dioxide) adduct), diaryliodonium salts under green LEDs (light emitting diode, Scheme 1a). Very recently, Li's group^[4a] reported a visible-light-induced oxidative cyclization of N-propargyl anilines with sulfinic acids using pyridine as base (Scheme 1b). Although a few synthetic methods have been developed, stoichiometric oxidants, relatively high temperatures, additional photocatalysts or additional base would limit their applications in synthetic chemistry.

  图式 1

  

  Scheme 1.  Visible-light-induced methods for the synthesis of 3-sulfonated quinoline derivatives from N-propargylamines

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  Sulfonohydrazide is a cheap and stable sulfonyl source.^[6] It can be easily transformed into sulfonyl radicals by using of tert-butyl hydroperoxide (TBHP) and give a new route to produce S-containing organic compounds.^[7] It is still an attractive but challenging task to explore a more convenient and mild method to access C₃-sulfonated quinolines from more common and inexpensive starting materials.

  2.   Results and discussion

  We began our research with the reaction of N-(3-phen- ylprop-2-yn-1-yl)aniline (1a) and 4-methyl-benzenesulfo- no-hydrazide (2a) in 1, 2-dichloroethane (DCE) by using TBHP as the oxidant under LED (435~440 nm, 7 W) irradiation in open air for 8 h without any photocatalyst and the desired product 4-phenyl-3-tosylquinoline (3a) was obtained in 89% isolated yield (Table 1, Entry 1). Inspired by this result, a series of oxidants were further researched (Table 1, Entries 2~4), and TBHP was proved to be the best oxidant. The use of the other solvents resulted in lower yields (Table 1, Entries 5~10). The light sources were then studied. However, LED (455~460 nm), LED (565~570 nm), LED (390~395 nm) and white light could not improve the reaction yield (Table 1, Entries 11~14). Subsequently, the reaction atmospheres were screened (Table 1, Entries 15, 16), such as N₂ and O₂, but the yields were not improved. Finally, the reaction temperature was increased to 40 ℃, and the corresponding product 3a was isolated in 86% yield (Table 1, Entry 17). No product 3a was generated when the reaction underwent in dark (Table 1, Entry 18). Based on all of the above results, the primary conditions were still selected as the optimized reaction conditions, namely, treatment of compound 1a with 1.75 equiv. of 2a, 2.5 equiv. of TBHP in DCE (0.25 mol•L^－1) at room temperature under blue LEDs (435~437 nm, 7 W) irradiation in open air for 8 h.

  表 1

  

  Table 1.  Optimization of the reaction conditions^a

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  Entry	Variations from standard conditions	Yieldb/%
  1	—	90
  2	DTBP instead of TBHP	Trace
  3	H2O2 instead of TBHP	Trace
  4	BPO instead of TBHP	20
  5	H2O instead of DCE	35
  6	Dioxane instead of DCE	32
  7	Dichloromethane instead of DCE	50
  8	CH3CN instead of DCE	10
  9	CH2Br2 instead of DCE	55
  10	Dimethylformamide instead of DCE	Trace
  11	455~460 nm instead of 435~440 nm	65
  12	565~570 nm instead of 435~440 nm	63
  13	390~395 nm instead of 435~440 nm	28
  14	White LED instead of 435~440 nm	30
  15	N2 instead of air	87
  16	O2 instead of air	85
  17	40 ℃ instead of room temperature	86
  18	In dark	Trace
  a Reaction conditions: 1a (0.2 mmol), 2a (0.35 mmol), TBHP (dry, 2.5 equiv.) in DCE (2 mL) and at room temperature under LEDs irradiation in open air for 8 h. b Yield of isolated product. DTBP＝Di-t-butyl peroxide; TBHP＝tert-Butyl hydroperoxide solution; BPO＝Dibenzoyl peroxide.

  Having the optimized reaction conditions in hand, the reactions of 4-methylbenzene-sulfonohydrazide with a variety of N-propargylanilines were investigated (Table 2). A series of of N-propargylanilines (1) were successfully reacted with 4-methylbenzenesulfono-hydrazide (2a) to generate the corresponding 3-sulfonated quinoline derivatives in good to excellent yields. First, the substitution pattern on the aromatic ring of the aniline group was investigated. Electron-donating groups on the aromatic ring provided the desired products in excellent yields (3b~3e). Electron-withdrawing groups on the benzene ring performed well in this transformation and smoothly produced the corresponding products in good yields (3f~3j). It is noteworthy that N-(3-phenylprop-2-yn-1-yl)-[1, 1'-biphen-yl]-2-amine performed well in this reaction, producing the product 3k in 72% yield. Subsequently, the influence of the substituents on the phenyl ring of the aromatic alkyne moiety was also explored. Substrates bearing electron- donating (OMe) or electron-withdrawing (Cl, F, and Ac) groups on the benzene ring that is directly bound to the triple bond all provided the corresponding products in satisfactory yields. It suggested that the substituted groups did not have a transformation influence on the reaction (3l~3o).

  表 2

  

  Table 2.  Scope of N-propargylanilines^{a, b}

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  a Reaction conditions: 1 (0.2 mmol), 2a (0.35 mmol), TBHP (dry, 2.5 equiv.) in DCE (2 mL) and at room temperature under blue LEDs (435~440 nm, 7 W) irradiation in open air for 8 h. b Yield of isolated product.

  Subsequently, the scope of sulfonyl hydrazides was also examined under the optimized reaction conditions. As shown in Table 3, various sulfonyl hydrazides including substituted groups (R＝H, OMe, t-Bu, OCF₃, F, Cl, Br, CO₂Et and Ph) at the para-position of the aromatic ring reacted with 1a to give the corresponding products (4a~4i) in 76%~87% yields. Additionally, 3-methylbenzene-sul- fonohydrazide and 2-methylbenzenesulfono-hydrazide were also effective in producing the desired 4-phenyl-3- (m-tolylsulfonyl)quinoline (4j) in 76% yield and 4-phenyl- 3-(o-tolylsulfonyl)quinoline (4k) in 78% yield. Notably, naphthalene-2-sulfonohydrazide could also perform well in this reaction, producing the product 4l in 76% yield. Moreover, thiophene-2-sulfonohydrazide was also evaluated, and the product 4m was obtained in a satisfactory yield. Surprisely, aliphatic sulfonyl hydrazides were also successfully employed under the standard conditions. Methanesulfonohydrazide and cyclopropane-sulfonohydra- zide smoothly underwent the reaction to produce the corresponding 3-sulfonated quinolines (4n and 4o) which could not be synthesized in the reported lit.erature.^[4a-4b]

  表 3

  

  Table 3.  Scope of arylsulfonylhydrazides^{a, b}

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  a Reaction conditions: 1a (0.2 mmol), 2 (0.35 mmol), TBHP (dry, 2.5 equiv.) in DCE (2 mL) and at room temperature under blue LEDs (435~440 nm, 7 W) irradiation in open air for 8 h. b Yield of isolated product.

  Control reactions between N-(3-phenylprop-2-yn- 1-yl)aniline (1a) and 4-methylbenzenesulfonohydrazide (2a) were conducted to get better understanding of the mechanistic pathway for the reaction (Scheme 2). When 2 equiv. of TEMPO was added to the reaction, the transfomation was completely restrained suggesting that the reaction might proceed via radical processes (Scheme 2a).

  图式 2

  

  Scheme 2.  Experiments for the mechanistic study

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  In the absence of 4-methylbenzene-sulfonohydrazide, no 4-phenylquinolone was observed, suggesting that the addition to the carbon-carbon triple bond might be prior to the cyclization of N-propargylaniline (Scheme 2b). Finally, the reaction of TsNHNH₂ with N-(3-phenylprop-2-yn-1- ylidene)-aniline could not produce 3a under the optimized conditions (Scheme 2c), thus illustrating that N-(3-phenyl-prop-2-yn-1-ylidene)aniline might not be an intermediate in this transfomation.

  On the basis of the above results and previous reports, ^[4] a plausible mechanism is proposed (Scheme 3). Firstly, sulfonyl radical is generated under visible-light irradiation and TBHP. Then, sulfonyl radical goes through intermolecular addition onto N-(3-phenylprop-2-yn-1-yl)-aniline to generate alkenyl radical A. Followed by the intramolecular attack of radical A on the pendant benzene ring subsequently produces intermediate B. Oxidation of B generates the corresponding cyclohexadienyl cation C, which undergoes deprotonation to provide 4-phenyl-3-tosyl-1, 2- dihydroquinoline (D). In the end, intermediate D ultimately aromatizes to afford the final product 3a.

  图式 3

  

  Scheme 3.  Tentative mechanistic pathway

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  3.   Conclusions

  In conclusion, we have developed a simple route to 3-sulfonated quinoline derivatives. This protocol was performed effectively at room temperature which involved cheap, readily available arylsulfonylhydrazides and low Watt blue LEDs. Moreover, this strategy exhibits good functional group tolerance, which can be used to afford various 3-sulfonated quinoline derivatives.

  4.   Experimental section

  4.1   Instruments and reagents

  Commercially available reagents were of reagent grade (AR grade) and were used without further purification. Reactions were monitored by thin layer chromatography (TLC) using silicycle pre-coated silica gel plates. Flash column chromatography was performed over silicycle silica gel (200~300 mesh). ¹H NMR and ¹³C NMR spectra were recorded on 400 MHz NMR plus spectrometer using residue solvent peaks as internal standards. Infrared spectra were recorded with IR spectrometer and were reported in reciprocal centimeter (cm^－1). High-resolution mass spectra (HRMS) were obtained with a Q-TOFPremier (ESI).

  4.2   Typical experimental procedure for the prepration of 3 or 4

  N-(3-Phenyl-2-propynyl)aniline derivatives 1 (0.2 mmol), sulfonohydrazides 2 (0.4 mmol), TBHP (dry, 0.7 mmol), and DCE (2.0 mL) were sequentially added to a 10 mL oven-dried reaction vessel at room temperature. The reaction vessel was exposed to blue LED (435~440 nm, 7 W) irradiation at room temperature in open air with stirring for 8 h. After completion of the reaction, the mixture was concentrated to yield the crude product, which was further purified by flash chromatography (silica gel, petroleum ether/ethyl acetate, V:V＝10:1) to give the desired products 3 or 4.

  4-Phenyl-3-tosylquinoline (3a):^[4e] Light yellow solid (64.6 mg, 90% yield), m.p. 173~175 ℃ (lit.^[4e] 172.6~174.3 ℃); ¹H NMR (500 MHz, CDCl₃) δ: 9.77 (s, 1H), 8.20 (dd, J＝8.6, 1.5 Hz, 1H), 7.84~7.76 (m, 1H), 7.46~7.41 (m, 2H), 7.34~7.29 (m, 3H), 7.19 (d, J＝8.5 Hz, 2H), 7.03 (d, J＝8.1 Hz, 2H), 6.96~6.92 (m, 2H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.89, 149.62, 147.70, 144.04, 137.91, 132.63, 132.59, 132.18, 130.00, 129.58, 129.24, 128.66, 127.92, 127.83, 127.64, 127.51, 127.42, 21.56.

  6-Methyl-4-phenyl-3-tosylquinoline (3b):^[4e] Light yellow solid (63.4 mg, 85% yield), m.p. 199~201 ℃ (lit.^[4e] 200.5~202.9 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.61 (s, 1H), 8.08 (d, J＝9.2 Hz, 1H), 7.46~7.41 (m, 2H), 7.32 (t, J＝7.7 Hz, 2H), 7.19 (d, J＝8.5 Hz, 2H), 7.06~7.01 (m, 2H), 6.97~6.90 (m, 2H), 6.49 (d, J＝2.9 Hz, 1H), 3.58 (s, 3H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 158.58, 148.03, 146.07, 145.33, 143.94, 138.06, 132.93, 132.87, 131.01, 129.91, 129.21, 128.84, 128.61, 127.91, 127.77, 124.81, 104.79, 55.34, 21.55.

  6-Ethyl-4-phenyl-3-tosylquinoline (3c): Light yellow solid (66.6 mg, 86% yield), m.p. 215~217 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.71 (s, 1H), 8.11 (d, J＝8.6 Hz, 1H), 7.67 (dd, J＝8.6, 2.0 Hz, 1H), 7.47~7.42 (m, 1H), 7.32 (t, J＝7.8 Hz, 2H), 7.18 (d, J＝8.4 Hz, 2H), 7.06~7.01 (m, 3H), 6.96~6.92 (m, 2H), 2.63 (q, J＝7.4 Hz, 2H), 2.33 (s, 3H), 1.12 (t, J＝7.6 Hz, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.22, 148.58, 146.89, 144.25, 143.91, 138.08, 133.38, 132.76, 132.56, 130.04, 129.47, 129.19, 128.56, 127.88, 127.61, 127.54, 124.81, 28.97, 21.55, 15.30. HRMS (ESI) calcd for C₂₄H₂₂NO₂S [M+H]⁺ 388.1366; found, 388.1369.

  7-Methyl-4-phenyl-3-tosylquinoline (3d):^[4a] Light yellow solid (67.1 mg, 90% yield), m.p. 205~207 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.79 (s, 1H), 8.09 (dd, J＝8.5, 1.7 Hz, 1H), 7.66 (dd, J＝8.5, 7.1 Hz, 1H), 7.27~7.25 (m, 1H), 7.21~7.17 (m, 3H), 7.11 (d, J＝8.4 Hz, 2H), 7.03~6.99 (m, 2H), 6.93~6.91 (m, 2H), 2.33 (s, 3H), 1.71 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 151.28, 150.36, 147.19, 143.77, 138.30, 138.08, 135.27, 133.54, 131.95, 131.72, 130.67, 129.21, 129.15, 128.62, 127.90, 127.57, 127.20, 23.95, 21.56.

  8-Methyl-4-phenyl-3-tosylquinoline (3e):^[4e] Light yellow solid (67.9 mg, 91% yield), m.p. 172~174 ℃ (lit.^[4e] 168.2~174.0 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.78 (s, 1H), 7.65 (d, J＝7.0 Hz, 1H), 7.46~7.42 (m, 1H), 7.34~7.29 (m, 3H), 7.20 (d, J＝8.5 Hz, 2H), 7.17~7.14 (m, 1H), 7.04 (d, J＝8.0 Hz, 2H), 6.95~6.92 (m, 2H), 2.86 (s, 3H), 2.34 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.91, 148.68, 146.53, 143.96, 138.09, 137.57, 133.08, 132.37, 132.28, 130.06, 129.23, 128.53, 127.95, 127.57, 127.55, 127.51, 125.42, 21.57, 18.25.

  6-Bromo-4-phenyl-3-tosylquinoline (3f):^[4e] Light yellow solid (71.7 mg, 82% yield), m.p. 199~202 ℃ (lit.^[4e] 201.2~203.6 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.76 (s, 1H), 8.05 (d, J＝8.9 Hz, 1H), 7.85 (dd, J＝8.9, 2.2 Hz, 1H), 7.50~7.41 (m, 2H), 7.33 (t, J＝7.8 Hz, 2H), 7.17 (d, J＝8.4 Hz, 2H), 7.04 (d, J＝7.9 Hz, 2H), 6.95~6.90 (m, 2H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.85, 148.32, 148.09, 144.27, 137.59, 135.60, 133.54, 131.87, 131.33, 129.96, 129.33, 129.01, 128.76, 127.95, 127.89, 122.28, 21.60.

  1-(4-Phenyl-3-tosylquinolin-6-yl)ethanone (3g): Light yellow solid (62.6 mg, 78% yield), m.p. 218~220 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.61 (s, 1H), 8.08 (d, J＝9.2 Hz, 1H), 7.46~7.40 (m, 2H), 7.34~7.29 (m, 2H), 7.19 (d, J＝8.5 Hz, 2H), 7.06~7.00 (m, 2H), 6.95~6.91 (m, 2H), 6.49 (d, J＝2.9 Hz, 1H), 3.58 (s, 3H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 167.70, 158.58, 148.03, 146.07, 145.33, 143.94, 138.06, 132.93, 132.87, 131.01, 129.91, 129.21, 128.84, 128.61, 127.91, 127.77, 124.81, 104.79, 55.34, 21.55. HRMS (ESI) calcd for C₂₄H₂₀NO₃S [M+H]⁺ 402.1158; found, 402.1155.

  6-Chloro-4-phenyl-3-tosylquinoline (3h):^[4e] Light yellow solid (68.4 mg, 87% yield), m.p. 187~189 ℃ (lit.^[4e] 185.9~187.3 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.75 (s, 1H), 8.13 (d, J＝9.0 Hz, 1H), 7.72 (dd, J＝9.0, 2.3 Hz, 1H), 7.47 (t, J＝7.6 Hz, 1H), 7.33 (t, J＝7.8 Hz, 2H), 7.26 (d, J＝2.3 Hz, 1H), 7.17 (d, J＝8.5 Hz, 2H), 7.06~7.01 (m, 2H), 6.94~6.90 (m, 2H), 2.34 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.99, 148.18, 148.03, 144.33, 137.66, 134.08, 133.63, 133.10, 131.99, 131.33, 130.00, 129.38, 129.05, 128.41, 128.01, 127.94, 126.06, 21.65.

  6-Fluoro-4-phenyl-3-tosylquinoline (3i):^[4e] Light yellow solid (68.6 mg, 91% yield), m.p. 172~174 ℃ (lit.^[4e] 173.3~176.7 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.72 (s, 1H), 8.19 (dd, J＝9.3, 5.4 Hz, 1H), 7.56 (ddd, J＝9.3, 7.8, 2.8 Hz, 1H), 7.48~7.42 (m, 1H), 7.33 (t, J＝7.9 Hz, 2H), 7.18 (d, J＝8.4 Hz, 2H), 7.07~7.01 (m, 2H), 6.94~6.87 (m, 3H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 162.03, 160.04, 149.14, 149.09, 147.10, 147.08, 146.86, 144.22, 137.63, 133.38, 132.26, 132.19, 129.84, 129.28, 128.90, 128.69, 128.62, 127.94, 127.90, 127.84, 122.55, 122.35, 110.79, 110.60, 21.55.

  7-Chloro-4-phenyl-3-tosylquinoline (3j): Light yellow solid (66.0 mg, 84% yield), m.p. 198~200 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.84 (s, 1H), 8.16 (dd, J＝8.5, 1.4 Hz, 1H), 7.68 (dd, J＝8.5, 7.5 Hz, 1H), 7.53 (dd, J＝7.5, 1.4 Hz, 1H), 7.37~7.34 (m, 1H), 7.16 (dd, J＝8.3, 7.6 Hz, 2H), 7.10 (d, J＝8.5 Hz, 2H), 7.03~6.99 (m, 2H), 6.91~6.87 (m, 2H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 151.44, 149.67, 148.17, 143.99, 137.80, 134.71, 133.41, 132.62, 131.77, 131.53, 130.68, 130.02, 129.25, 128.55, 127.64, 126.96, 124.27, 21.57. HRMS (ESI) calcd for C₂₂H₁₇ClNO₂S [M+H]⁺ 394.0663; found 394.0661.

  4, 8-Diphenyl-3-tosylquinoline (3k): Light yellow solid (62.6 mg, 72% yield), m.p. 199~201 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.78 (s, 1H), 7.65 (d, J＝7.0 Hz, 1H), 7.46~7.42 (m, 1H), 7.34~7.29 (m, 3H), 7.20 (d, J＝8.5 Hz, 2H), 7.17~7.14 (m, 1H), 7.04 (d, J＝8.0 Hz, 2H), 6.95~6.92 (m, 2H), 2.86 (s, 3H), 2.34 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.91, 148.68, 146.53, 143.96, 138.09, 137.57, 133.08, 132.37, 132.28, 130.06, 129.23, 128.53, 127.95, 127.57, 127.55, 127.51, 125.42, 21.57, 18.25. HRMS (ESI) calcd for C₂₈H₂₂NO₂S [M+H]⁺ 436.1366; found 436.1367.

  4-(4-Methoxyphenyl)-3-tosylquinoline (3l):^[4e] Light yellow solid (58.4 mg, 75% yield), m.p. 161~164 ℃; (lit.^[4e] 159.2~160.8 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.75 (s, 1H), 8.18 (dt, J＝8.5 Hz, 1.0, 1H), 7.79 (ddd, J＝8.4, 6.7 Hz, 1.5, 1H), 7.44 (ddd, J＝8.0, 6.8, 1.3 Hz, 1H), 7.38 (ddd, J＝8.6, 1.6, 0.7 Hz, 1H), 7.21 (d, J＝8.5 Hz, 2H), 7.07~7.02 (m, 2H), 6.88~6.83 (m, 4H), 3.89 (s, 3H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 159.93, 149.99, 149.66, 147.74, 143.96, 137.97, 133.02, 132.09, 131.39, 129.58, 129.15, 127.92, 127.86, 127.74, 127.42, 124.58, 113.10, 55.40, 21.55.

  4-(4-Chlorophenyl)-3-tosylquinoline (3m):^[4a] Light yellow solid (60.5 mg, 77% yield), m.p. 192~194 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.75 (s, 1H), 8.13 (d, J＝9.0 Hz, 1H), 7.72 (dd, J＝9.0, 2.3 Hz, 1H), 7.47 (t, J＝7.6, 1H), 7.33 (t, J＝7.8 Hz, 2H), 7.26 (d, J＝2.3 Hz, 1H), 7.17 (d, J＝8.5 Hz, 2H), 7.06~7.01 (m, 2H), 6.94~6.90 (m, 2H), 2.34 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.99, 148.18, 148.03, 144.33, 137.66, 134.08, 133.63, 133.10, 131.99, 131.33, 130.00, 129.38, 129.05, 128.41, 128.01, 127.94, 126.06, 21.65.

  4-(4-Bromophenyl)-3-tosylquinoline (3n):^[4a] Light yellow solid (76.9 mg, 88% yield), m.p. 198~200 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.76 (s, 1H), 8.05 (d, J＝8.9 Hz, 1H), 7.85 (dd, J＝8.9 Hz, 2.2, 1H), 7.50~7.41 (m, 2H), 7.33 (t, J＝7.8 Hz, 2H), 7.17 (d, J＝8.4 Hz, 2H), 7.04 (d, J＝7.9 Hz, 2H), 6.95~6.90 (m, 2H), 2.33 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 148.85, 148.32, 148.09, 144.27, 137.59, 135.60, 133.54, 131.87, 131.33, 129.96, 129.33, 129.01, 128.76, 127.95, 127.89, 122.28, 21.60.

  1-(4-(3-Tosylquinolin-4-yl)phenyl)ethanone (3o):^[4e] Light yellow solid (73.0 mg, 91% yield), m.p. 201~203 ℃ (lit.^[4e] 202.5~204.6 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.71 (s, 1H), 8.11 (d, J＝8.6 Hz, 1H), 7.67 (dd, J＝8.6, 2.0 Hz, 1H), 7.47~7.42 (m, 1H), 7.32 (t, J＝7.8 Hz, 2H), 7.18 (d, J＝8.4 Hz, 2H), 7.06~7.01 (m, 3H), 6.96~6.92 (m, 2H), 2.63 (q, J＝7.4 Hz, 2H), 2.33 (s, 3H), 1.12 (t, J＝7.6 Hz, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.22, 148.58, 146.89, 144.25, 143.91, 138.08, 133.38, 132.76, 132.56, 130.04, 129.47, 129.19, 128.56, 127.88, 127.61, 127.54, 124.81, 28.97, 21.55, 15.30.

  4-Phenyl-3-(phenylsulfonyl)quinoline (4a):^[4e]: Light yellow solid (56.6 mg, 82% yield), m.p. 187~189 ℃ (lit.^[4e] 187.8~189.4 ℃); ¹H NMR (400 MHz, Chloroform-d) δ: 9.72 (s, 1H), 8.15 (d, J＝8.1 Hz, 1H), 7.78~7.69 (m, 1H), 7.37~7.32 (m, 3H), 7.24~7.13 (m, 7H), 6.83 (d, J＝8.1 Hz, 2H); ¹³C NMR (101 MHz, CDCl₃) δ: 150.29, 149.58, 147.53, 140.77, 134.24, 133.06, 132.44, 130.07, 130.02, 128.75, 128.67, 128.00, 127.89, 127.76, 127.50.

  3-((4-Methoxyphenyl)sulfonyl)-4-phenylquinoline

  (4b):^[4e] Light yellow solid (60.0 mg, 80% yield), m.p. 170~172 ℃ (lit.^[4e] 167.1~168.9 ℃); ¹H NMR (500 MHz, Chloroform-d) δ: 9.77 (s, 1H), 8.19 (dt, J＝8.5, 1.0 Hz, 1H), 7.79 (ddd, J＝8.4, 6.8, 1.4 Hz, 1H), 7.46~7.40 (m, 2H), 7.37~7.30 (m, 3H), 7.22 (d, J＝8.9 Hz, 2H), 6.99~6.95 (m, 2H), 6.70 (d, J＝9.0 Hz, 2H), 3.79 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 163.27, 149.64, 147.74, 132.93, 132.74, 132.45, 132.08, 130.15, 130.07, 129.63, 128.67, 127.80, 127.70, 127.54, 127.40, 113.88, 55.66.

  3-((4-(Tert-butyl)phenyl)sulfonyl)-4-phenylquinoline

  (4c): Light yellow solid (61.8 mg, 77% yield), m.p. 168~170 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.77 (s, 1H), 8.19 (dt, J＝8.5, 1.0 Hz, 1H), 7.79 (ddd, J＝8.4, 6.8, 1.4 Hz, 1H), 7.46~7.40 (m, 2H), 7.37~7.30 (m, 3H), 7.22 (d, J＝8.9 Hz, 2H), 6.99~6.95 (m, 2H), 6.70 (d, J＝9.0 Hz, 2H), 3.79 (s, 3H); ¹³C NMR (126 MHz, CDCl₃) δ: 163.27, 149.64, 147.74, 132.93, 132.74, 132.45, 132.08, 130.15, 130.07, 129.63, 128.67, 127.80, 127.70, 127.54, 127.40, 113.88, 55.66. HRMS (ESI) calcd for C₂₅H₂₄NO₂S [M+H]⁺ 402.1522; found 402.1518.

  4-Phenyl-3-((4-(trifluoromethoxy)phenyl)sulfonyl)quinoline (4d):^[4e] Light yellow solid (66.9 mg, 78% yield), m.p. 161~165 ℃ (lit.^[4e] 162.2~165.7 ℃); ¹H NMR (400 MHz, Chloroform-d) δ: 9.80 (s, 1H), 8.23 (d, J＝8.4 Hz, 1H), 7.89~7.80 (m, 1H), 7.50~7.43 (m, 2H), 7.35~7.29 (m, 5H), 7.07~7.02 (m, 2H), 6.96~6.91 (m, 2H); ¹³C NMR (101 MHz, CDCl₃) δ: 152.30, 152.29, 150.13, 149.77, 147.24, 138.95, 132.61, 132.35, 132.06, 130.09, 130.06, 129.64, 128.93, 128.14, 127.85, 127.42, 127.37, 120.57.

  3-((4-Fluorophenyl)sulfonyl)-4-phenylquinoline (4e):^[4e] Light yellow solid (63.2 mg, 87% yield), m.p. 181~183 ℃ (lit.^[4e] 180~182.3 ℃); ¹H NMR (400 MHz, Chloroform-d) δ: 9.79 (s, 1H), 8.28~8.19 (m, 1H), 7.89~7.77 (m, 1H), 7.51~7.44 (m, 2H), 7.38~7.27 (m, 5H), 7.00~6.87 (m, 4H); ¹³C NMR (101 MHz, CDCl₃) δ: 166.57, 164.02, 150.13, 149.64, 147.37, 136.73, 132.54, 132.44, 132.29, 130.81, 130.71, 130.09, 129.59, 128.91, 128.09, 127.85, 127.44, 116.05, 115.82.

  3-((4-Chlorophenyl)sulfonyl)-4-phenylquinoline (4f):^[4e] Light yellow solid (65.2 mg, 86% yield), m.p. 168~170 ℃ (lit.^[4e] 167.1~170.2 ℃); ¹H NMR (400 MHz, Chloroform-d) δ: 9.78 (s, 1H), 8.27~8.21 (m, 1H), 7.86~7.82 (m, 1H), 7.51~7.45 (m, 2H), 7.38~7.32 (m, 3H), 7.21 (s, 4H), 6.98~6.92 (m, 2H); ¹³C NMR (101 MHz, CDCl₃) δ: 150.25, 149.63, 147.33, 139.81, 139.19, 132.61, 132.37, 132.12, 130.09, 129.56, 129.34, 128.95, 128.92, 128.13, 127.85, 127.45.

  3-((4-Bromophenyl)sulfonyl)-4-phenylquinoline (4g):^[4e] Light yellow solid (71.1 mg, 84% yield), m.p. 250~253 ℃ (lit.^[4e] 252.2~253.8 ℃); ¹H NMR (400 MHz, Chloroform-d) δ: 9.79 (s, 1H), 8.28~8.19 (m, 1H), 7.89~7.77 (m, 1H), 7.51~7.44 (m, 2H), 7.38~7.27 (m, 5H), 7.00~6.87 (m, 4H); ¹³C NMR (101 MHz, CDCl₃) δ: 166.57, 164.02, 150.13, 149.64, 147.37, 136.73, 132.54, 132.44, 132.29, 130.81, 130.71, 130.09, 129.59, 128.91, 128.09, 127.85, 127.44, 116.05, 115.82.

  Ethyl 4-((4-phenylquinolin-3-yl)sulfonyl)benzoate (4h): Light yellow solid (63.4 mg, 76% yield), m.p. 265~267 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 9.80 (s, 1H), 8.24 (d, J＝8.6 Hz, 1H), 7.92~7.80 (m, 3H), 7.49~7.45 (m, 2H), 7.37~7.29 (m, 5H), 6.96~6.88 (m, 2H), 4.38 (q, J＝7.1 Hz, 2H), 1.38 (t, J＝7.2 Hz, 3H); ¹³C NMR (101 MHz, CDCl₃) δ: 165.00, 150.47, 149.73, 147.41, 144.47, 134.36, 132.66, 132.23, 131.84, 130.06, 129.67, 129.60, 128.97, 128.14, 127.87, 127.83, 127.47, 127.42, 61.81, 14.24. HRMS (ESI) calcd for C₂₄H₂₀NO₄S [M+ H]⁺ 418.1108; found 418.1109.

  3-([1, 1'-Biphenyl]-4-ylsulfonyl)-4-phenylquinoline (4i): Light yellow solid (65.7 mg, 78% yield), m.p. 187~189 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.83 (s, 1H), 8.21 (d, J＝1.5 Hz, 1H), 7.86~7.78 (m, 1H), 7.53~7.50 (m, 2H), 7.48~7.43 (m, 6H), 7.42~7.39 (m, 1H), 7.38~7.30 (m, 5H), 7.00~6.95 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.90, 149.79, 147.65, 145.91, 139.31, 139.14, 132.62, 132.55, 132.26, 130.09, 129.69, 129.08, 128.71, 128.65, 128.39, 127.90, 127.73, 127.49, 127.44, 127.28, 127.23. HRMS (ESI) calcd for C₂₇H₂₀NO₂S [M+ H]⁺ 422.1209; found, 422.1205.

  4-Phenyl-3-(m-tolylsulfonyl)quinoline (4j):^[4a] Light yellow solid (54.6 mg, 76% yield), m.p. 156~159 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.83 (s, 1H), 8.21 (d, J＝1.5 Hz, 1H), 7.86~7.78 (m, 1H), 7.53~7.50 (m, 2H), 7.48~7.43 (m, 6H), 7.42~7.39 (m, 1H), 7.38~7.30 (m, 5H), 7.00~6.95 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.90, 149.79, 147.65, 145.91, 139.31, 139.14, 132.62, 132.55, 132.26, 130.09, 129.69, 129.08, 128.71, 128.65, 128.39, 127.90, 127.73, 127.49, 127.44, 127.28, 127.23.

  4-Phenyl-3-(o-tolylsulfonyl)quinoline (4k): Light yellow solid (56.0 mg, 78% yield), m.p. 152~154 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 9.82 (s, 1H), 8.24 (d, J＝8.4 Hz, 1H), 7.87~7.78 (m, 1H), 7.46 (ddd, J＝8.2, 6.8, 1.2 Hz, 1H), 7.34~7.27 (m, 3H), 7.19 (t, J＝7.9 Hz, 2H), 7.14 (dd, J＝8.0, 1.5 Hz, 1H), 7.08~7.05 (m, 1H), 6.93~6.87 (m, 1H), 6.87~6.82 (m, 2H), 2.24 (s, 3H); ¹³C NMR (101 MHz, CDCl₃) δ: 149.79, 149.50, 147.91, 138.53, 136.70, 133.18, 132.30, 132.20, 132.09, 131.87, 129.66, 129.63, 129.31, 128.57, 127.98, 127.63, 127.41, 127.37, 126.03, 20.00. HRMS (ESI) calcd for C₂₂H₁₈NO₂S [M+H]⁺ 360.1053; found 360.1051.

  3-(Naphthalen-2-ylsulfonyl)-4-phenylquinoline (4l):^[4a] Light yellow solid (60.0 mg, 76% yield), m.p. 155~157 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.87 (s, 1H), 8.25~8.19 (m, 1H), 7.83~7.78 (m, 2H), 7.74~7.66 (m, 3H), 7.62~7.59 (m, 1H), 7.55 (ddd, J＝8.1, 6.9, 1.3 Hz, 1H), 7.45~7.35 (m, 3H), 7.29 (dd, J＝8.5, 1.9 Hz, 1H), 7.20~7.14 (m, 2H), 6.90~6.84 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ: 150.18, 149.83, 147.80, 137.35, 134.87, 132.39, 132.30, 132.23, 131.73, 130.23, 130.02, 129.69, 129.54, 129.19, 129.01, 128.85, 127.88, 127.80, 127.60, 127.50, 127.43, 127.41, 122.45.

  4-Phenyl-3-(thiophen-2-ylsulfonyl)quinoline (4m):^[4a] Light yellow solid (55.5 mg, 79% yield), m.p. 193~195 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 7.66 (d, J＝8.3 Hz, 2H), 7.32 (s, 1H), 7.23 (d, J＝8.2 Hz, 2H), 7.18 (d, J＝8.8 Hz, 2H), 7.03 (d, J＝8.8 Hz, 2H), 2.38 (s, 3H); ¹³C NMR (101 MHz, CDCl₃) δ: 144.33, 135.67, 135.25, 130.92, 129.91, 129.51, 127.37, 122.94, 21.70.

  3-(Methylsulfonyl)-4-phenylquinoline (4n): White solid (37.9 mg, 67% yield), m.p. 88~90 ℃; ¹H NMR (400 MHz, Chloroform-d) δ: 9.59 (s, 1H), 8.27~8.21 (m, 1H), 7.92~7.83 (m, 1H), 7.59~7.52 (m, 4H), 7.48 (dd, J＝8.5 Hz, 1.9, 1H), 7.44~7.40 (m, 2H), 2.77 (s, 3H); ¹³C NMR (101 MHz, CDCl₃) δ: 149.80, 149.68, 147.45, 132.93, 132.47, 131.67, 130.05, 129.72, 129.52, 128.28, 128.16, 127.69, 127.23, 44.53. HRMS (ESI) calcd for C₁₆H₁₃NO₂S [M+ H]⁺ 283.0667; found 283.0669.

  3-(Cyclopropylsulfonyl)-4-phenylquinoline (4o): White solid (48.2 mg, 78% yield), m.p. 95~97 ℃; ¹H NMR (500 MHz, Chloroform-d) δ: 9.49 (s, 1H), 8.23 (d, J＝8.5 Hz, 1H), 7.89~7.82 (m, 1H), 7.58~7.50 (m, 4H), 7.49~7.42 (m, 3H), 2.04 (tt, J＝8.0, 4.8 Hz, 1H), 1.18~1.12 (m, 2H), 0.89~0.81 (m, 2H); ¹³C NMR (126 MHz, CDCl₃) δ: 149.65, 149.41, 147.68, 133.50, 132.18, 132.05, 130.20, 129.72, 129.30, 128.04, 127.98, 127.71, 127.50, 32.95, 6.33. HRMS (ESI) calcd for C₁₈H₁₅NO₂S [M+H]⁺ 309.0823; found 309.0826.

  Supporting Information ¹H NMR and ¹³C NMR spectra of new compounds. The Supporting Information is available free of charge via the Internet at http://sioc-journal.cn/.

  
  
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• 

  Scheme 1  Visible-light-induced methods for the synthesis of 3-sulfonated quinoline derivatives from N-propargylamines

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  Scheme 2  Experiments for the mechanistic study

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  Scheme 3  Tentative mechanistic pathway

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  Table 1.  Optimization of the reaction conditions^a

  Entry	Variations from standard conditions	Yieldb/%
  1	—	90
  2	DTBP instead of TBHP	Trace
  3	H2O2 instead of TBHP	Trace
  4	BPO instead of TBHP	20
  5	H2O instead of DCE	35
  6	Dioxane instead of DCE	32
  7	Dichloromethane instead of DCE	50
  8	CH3CN instead of DCE	10
  9	CH2Br2 instead of DCE	55
  10	Dimethylformamide instead of DCE	Trace
  11	455~460 nm instead of 435~440 nm	65
  12	565~570 nm instead of 435~440 nm	63
  13	390~395 nm instead of 435~440 nm	28
  14	White LED instead of 435~440 nm	30
  15	N2 instead of air	87
  16	O2 instead of air	85
  17	40 ℃ instead of room temperature	86
  18	In dark	Trace
  a Reaction conditions: 1a (0.2 mmol), 2a (0.35 mmol), TBHP (dry, 2.5 equiv.) in DCE (2 mL) and at room temperature under LEDs irradiation in open air for 8 h. b Yield of isolated product. DTBP＝Di-t-butyl peroxide; TBHP＝tert-Butyl hydroperoxide solution; BPO＝Dibenzoyl peroxide.

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  Table 2.  Scope of N-propargylanilines^{a, b}

  a Reaction conditions: 1 (0.2 mmol), 2a (0.35 mmol), TBHP (dry, 2.5 equiv.) in DCE (2 mL) and at room temperature under blue LEDs (435~440 nm, 7 W) irradiation in open air for 8 h. b Yield of isolated product.

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  Table 3.  Scope of arylsulfonylhydrazides^{a, b}

  a Reaction conditions: 1a (0.2 mmol), 2 (0.35 mmol), TBHP (dry, 2.5 equiv.) in DCE (2 mL) and at room temperature under blue LEDs (435~440 nm, 7 W) irradiation in open air for 8 h. b Yield of isolated product.

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•