English

• 1.   Introduction

  Phenols work as versatile natural intermediates and are used as important synthetic building blocks for constructing pharmaceuticals, agrochemicals, additives, antioxidants, antiseptics and polymers^[1] since phenol possesses specific characteristics and plays an important role in re-dox reactions in nature. Diarylmethane is a valuable structural group of many important bioactive compounds such as sertraline, clemastine, nuvigil and lomerizine and it is useful structural moiety in organic synthesis and drug discovery. Because of these, some benzylated phenols like lasofoxifene, detrol, corlopam, agrimophol and etc., structurally associated with both of diarylmethane and phenol, are bioactive and used as drugs in clinic.

  Friedel-Craft reaction and its related reactions^[2] of arene with benzyl halides and cross-coupling^[3] of aryl halides or special arenes with benzyl compounds are two complementary synthetic routes for the synthesis of diarylmethane. However, these methods are sometimes not suitable for the synthesis of benzylated phenol due to phenol group. The rearrangement of benzyl aryl ether is a valuable method to generate benzylated phenol with diarylmethane skeleton and phenol group, which was first introduced by Hartmann and Gattermann more than 120 years ago^[4] and up to 1952, Tarbell and Petropoulos^[5] described in detail the rearrangement of benzyl phenyl ether. Afterwards, the rearrangement is attracting considerable efforts in the synthesis.^[6] Bode and co-workers^[7] demonstrated the arylation of BF₃•OEt₂-catalyzed benzyl hydroxamates. Paquin and coworkers^[8] developed the Friedel-Crafts alkylation of arenes with benzyl fluorides via the in situ generation of HF. And, later, Moran's group^[9] demonstrated the dehydrative Friedel-Crafts reactions of deactivated benzylic alcohols under super Br nsted acid catalysis. Antonchick's group^[10] disclosed a catalytic, metal-free intramolecular rearrangement of benzyl phenyl ethers using nitrosonium salt as a catalyst.

  The rearrangement of some specific benzyl aryl ethers with acidic catalysts can offer acceptable rearrangement results; however, there is a lack of systematic study in the field. For versatile access to benzylated phenols, it is established that benzyl aryl ethers undergo benzyl rearrangement under the catalysis of polyphosphoric acid (PPA). Herein, we present our systematic investigation on PPA-catalyzed rearrangement of benzyl aryl ether in moderate to good yield (Scheme 1).

  Scheme 1

  

  Scheme 1.  Synthesis of 1aa to 1al and reaction process of benzyl rearrangement

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  2.   Results and discussion

  2.1   Reaction conditions for PPA-catalyzed benzyl rearrangement

  The study of the benzyl rearrangement was first conducted at room temperature (ca. 25 ℃) by PPA-catalyzed reaction of 1-(4'-benzyloxy)-4-methoxybenzene (1aa)^[11a] and the reaction (Scheme 1 and Table 1, Entry 1) produced two rearranged products of 2aa (o)^{[11b, 12b]} as a major product (62% yield) and 2aa (m) ^[12b] as a minor product (7% yield), and trace amount of debenzylated product 3a. The rearranged position of 2aa (o) was determined by nuclear Overhauser effect spectroscopy (NOESY), in which there is nuclear Overhauser effect (NOE) between phenolic-OH and only one aromatic CH, NOE between CH₂ of Bn with one aromatic CH and weak NOE between phenolic-OH and CH₂ of Bn. Meanwhile, there are NOEs between OCH₃ with one or two aromatic CHs.

  Table 1

  

  Table 1.  Influence of catalysts and solvents on the benzyl rearrangement at 25 ℃

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  Entry	Catalyst	Solventa	Time/h	Ratiob/%
  				2aa (o)c	2aa (m)d	3a	Unreacted 1aa
  1e	PPA	DCE	72	62	7	Trace	Trace
  2	PPA	Dry DCM	180	60	10	10	20
  3	H3PO4 (≥85%)	DCE	60	NR	NR	NR	100
  4	PPTS	DCE	60	NR	NR	NR	100
  5	TsOH•H2O	DCE	60	NR	NR	NR	100
  6	TFA	DCE	126	40	10	30	10
  7	Cond. HCl	DCE	40	NR	NR	NR	100
  8	Cond. HCl	Dry DCM	80	NR	NR	NR	100
  9	Anhydrous AlCl3	Dry DCM	10	40	Trace	30	0
  10	Anhydrous ZnCl2	Dry DCM	168	NR	NR	Trace	> 95
  11e	PPA	Toluene	96	65	20	10	Trace
  12	PPA	THF	96	NR	NR	NR	100
  13	PPA	Dioxane	120	—	—	Trace	> 95
  14	PPA	DME	124	—	—	Trace	80
  15	PPA	Ethyl ether	96	NR	NR	NR	100
  a The solvent was used directly or treated for anhydrous goal before use. Asterisk (*) denotes minor regioisomer. b The ratio was estimated by TLC except Entries 1 and 11. —, NR, and trace represent not detectable, no reaction and lower than 5%, respectively. c ortho to hydroxy. d meta to hydroxy. e Isolated yields.

  To explore the reaction conditions, the rearrangement of 1aa was carried out in the presence of a series of acidic catalysts in different solvents at 25 ℃ (Table 1). As PPA in 1, 2-dichloroethane (DCE) (Table 1, Entry 1), PPA in dichloromethane (DCM) and toluene (Table 1, Entries 2, 11) also afforded 2aa (o) as a major product and 2aa (m) as a minor product with 10% yield of 3a. However, trifluoroacetic acid (TFA) in DCE (Table 1, Entry 6) catalyzed the reaction to produce 50% yield of 2aa (o) and 2aa (m) in total and 30% yield of 3a, and anhydrous AlCl₃ in DCM (Table 1, Entry 9) resulted in 40% yield of 2aa (o) and 30% yield of 3a. Anhydrous ZnCl₂ only produced trace amount of 3a (Table 1, Entry 10) and no reaction happened by H₃PO₄ (Table 1, Entry 3), pyridinium 4-toluene- sulfonate (PPTS) (Table 1, Entry 4), TsOH•H₂O (Table 1, Entry 5) and cond. HCl (Table 1, Entries 7 and 8). It is interesting and important that ether solvents (Table 1, Entries 17~20) of tetrahydrofuran (THF), dioxane, 1, 2-di- methoxyethane (DME) and ethyl ether were not benign solvents for the rearrangement catalyzed by PPA.

  In general, TFA and anhydrous AlCl₃ are not as effective as PPA in the benzyl rearrangement due to its production of appreciable 3a, and PPA was determined to be the optimal catalyst. The PPA-catalyzed rearrangement is tolerated solvents of DCE, DCM and toluene, and DCE was the first choice of the reaction solvent used in this study.

  2.2   Effects of substitutions at phenolic moiety

  The effects of the substitutions at phenolic moiety and benzyl moiety on the rearrangement reactivity are presented in Table 2.

  Table 2

  

  Table 2.  Effects of EWG and EDG substitutions at phenolic moiety on the rearrangement^a

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  The electron donating group (EDG) of OMe in benzyl moiety promotes the rearrangement and deprotection (Table 2), resulting that p-methoxybenzyl (PMB) (R²＝OMe) is more easily rearranged or/and deprotected than benzyl (Bn) (R²＝H) at lower temperature and in shorter reaction time, but the rearranged yields of Bn phenyl ethers 1aa, ^[11a] 1ba, ^[13a] 1ca, ^[15a] 1ea, ^[17] 1fa^[18a] and 1ga^[19a] are better than those of PMB phenyl ethers 1ab, ^[12a] 1bb, ^[14a] 1cb, ^[15b] 1eb, 1fb, ^[18c] and 1gb.^[19b] These results can be reasoned from higher stabilizing capacity of OMe for the formation of partial positive ion of PMB and on the other hand, more stable partial positive ion of PMB possesses less electrophilic ability than less stable partial positive ion of Bn (Scheme 1). It is noticed that the para to OH product 2ba (p)^[13b] was a minor product of Bn ether compound 1ba, ^[13a] while PMB ether compound 1bb^[14a] produced the para to OH product 2bb^[14b] as the sole product, and compound 1ca^[15a] (Table 2) proceeded the rearrangement in toluene to yield 2ca ^[15c] but no reaction happened in DCE.

  The EDG may not be helpful for the formation of the negative ion of phenolic oxygen, but it makes phenolic moiety more nucleophilic and readily accept the electrophilic attack by benzyl cation to establish the rearrangement of benzyl moiety (Table 2). Instead, electron withdrawing group (EWG) speeds up the formation of the negative ion of phenolic oxygen while it prevents phenolic moiety from being attacked by benzyl cation (Table 2). Compound 1fa^[18a] (Table 2) and compound 1fb^[18c] (Table 2) with a carboxylate group at phenolic moiety underwent the rearrangement, but 1fa^[18a] afforded much better yield of the rearranged product 2fa^[18b] than 1fb generated mono-rearranged product 2fba and bi-rearranged product 2fbb. Meanwhile, bearing cyano group at phenolic moiety, compound 1ga^[19a] gave approximately 40% yield of the rearranged product 2ga (Table 2) but compound 1gb^[19b] did not produce any rearranged product (Table 2).

  2.3   Influences of varied arenes and combined substitutions

  The effects of combined substitutions of EWGs and EDGs, substitution positions or varied arenes on the rearrangement were further investigated. Compared to compounds 1ia^[16] and 1ib^[21] (Table 2), introduction of an EDG of methoxy group made compound 1ja^[22a] undergo the rearrangement of benzyl group, but compound 1jb^[22b] produced the mixture and no detectable rearranged product of PMB group (Table 3). The same results as 1ja and 1jb happened for compounds 1ka^[23a] and 1kb, ^[23a] which 1ka gave rearranged product 2ka^[23b] but 1kb generated the mixture (Table 3). Compounds 1la (2'-methoxy), ^[24a] 1ma (3'-methoxy)^[11a] and 1na (2'-methyl)^[26a] smoothly underwent the rearrangement of benzyl group to afford products 2la (o)^[24b] (ortho to OH) and 2la (m)^[24c] (para to OMe), 2ma (o)^[25a] (ortho to OH and OMe) and 2ma (o')^[25b] (para to OMe), 2na (o)^[26b] (ortho to OH) and 2na (p)^[26c] (para to OH), respectively (Table 3). Product 2ma (o) has the identical ¹H NMR signal pattern of 3 aromatic C—Hs of phenolic moiety to the literature, ^[25a] in which 2ma (o) was prepared by other route. The regio-chemistry observations suggested that the regio-selectivity of these products obeyed the substitution directing rule at the aromatic ring.

  Table 3

  

  Table 3.  Influences of combined substitutions, substitution positions and varied arenes at phenolic moiety on the rearrangement^a

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  α-Naphtholate of Bn ether 1oa^[16] (Table 3) or PMB ether 1ob^[28a] (Table 3) displayed a good rearrangement reactivity to afford 2'-rearranged Bn product 2oa^[27] (ortho to OH) or 2'- and 4'-rearranged PMB products 2ob (o)^{[27, 28b]} (ortho to OH) and 2ob (p) (para to OH), respectively. Due to relatively lower reactivity of Bn, 56% unreacted 1oa were isolated. Meanwhile, β-naphtholate of benzyl ether 1pa^[29a] (Table 3) or PMB ether 1pb^[29a] (Table 3) produced 1'-(ortho to OH) product 2pa^[29b] or 1'-(ortho to OH) product 2pb.^[29b] These results suggest that the scope of phenolic moiety for the rearrangement is adaptable.

  2.4   Effects of benzyl groups on the rearrangement

  As 4'-OMe of PMB affected on the balance between the rearrangement and the deprotection (Tables 2, 3), other EDGs at benzyl moiety or benzyl-like moiety were explored (Table 4). As reported, allyl phenyl ether 1ac ^[30a] (Table 4) underwent the rearrangement in PPA to yield an ortho to OH product 2ac^[30b] in 39% yield. Interestingly, 2'-PMB ether 1ad (Table 4) gave better yield of rearranged product 2ad than 4'-PMB ether 1ab did (Table 2).

  Table 4

  

  Table 4.  Effects of benzyl groups or benzyl-like groups on the rearrangement^a

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  Introduction of EWG to aromatic moiety of benzyl moi- ety resulted in reducing the reactivity of these ethers, e.g., 4'- or 3'-nitro-benzyl compound 1ae^[31] or 1af, 4'-cyano- benzyl compound 1ag, and 4'-carboxylate benzyl compound 1ah^[18c] showed no reaction for the rearrangement and the deprotection (Table 4). Compared to EWG substitutions at phenolic moiety (Table 2), it is suggested that EWG substitutions at benzyl moiety more strongly affect the reactivity both for the rearrangement and the deprotection.

  The effects of menaphthyl group were also studied. Both of β-menaphthyl and α-menaphthyl phenyl ethers 1ai and 1aj^[32] smoothly underwent the rearrangement to produce ortho to OMe products 2ai and 2aj, respectively, which showed similar ¹H NMR patterns of phenolic C—H to product 2aa (m) (Table 2). We next extended "R³" from H to methyl and phenyl. Compound 1ak^[33a] (R³＝Me, Table 4) afforded as normal two rearranged products 2ak (o)^[33b] and 2ak (m). The ortho to OH product 2ak (o)^[33b], which ¹H NMR signal pattern of 3 aromatic C—Hs of phenolic moiety is identical to the literature ^[33b] and similar to 2aa (o) but not 2aa (m), was a major product, and the ortho to OMe product 2ak (m) was a minor product. Compound 1al^[34a] (R³＝Ph, Table 4) produced only 16% mono-rear- ranged product 2ala^[34b] but 23% bi-rearranged product 2alb, and both of 2ala^[34b] and 2alb are ortho to OMe products.

  3.   Conclusions

  In summary, the rearrangement activity of benzyl aryl ether catalyzed by PPA has been systematically investigated. In general, EWG substitutions at phenolic moiety (R¹＝EWG) or benzyl moiety (R², R³＝EWG) decelerate the rearrangement, and EDG substitutions at phenolic moiety (R¹＝EDG) exert a positive influence on the rearrangemen. However, EDG substitutions at benzyl moiety (R²＝EDG) exert a positive influence on both rearrangement and deprotection. Importantly, optimal tuning of the rearrangement activity by substitutions of EWG and EDG at phenolic moiety or benzyl moiety could be beneficial for the rearrangement, and the regio-selectivity of the rearrangement obeyed the substitution directing rule at the aromatic ring.

  4.   Experimental section

  4.1   General information

  ¹H NMR and ¹³C NMR spectra were recorded on a Bruker AV-400 spectrometer at 400 and 100 MHz, respectively, in indicated deuterated solvents. The low or high resolution of ESIMS was recorded on an Agilent 1200 HPLC-MSD mass spectrometer or Applied Biosystems Q-STAR Elite ESI-LCMS/ MS mass spectrometer, respectively. Melting points were measured using an YRT-3 melting point apparatus and were uncorrected.

  4.2   General synthetic procedure for the unknown starting materials of ether compounds

  Phenol (1.0 mmol) was dissolved in 10 mL of acetonitrile and then 1.2 mmol of allyl chloride, ethyl chloroacetate, benzyl chloride/bromide, PMB chloride/bromide or the related chloride/bromide analogues was added. The reaction mixture was monitored by TLC and generally refluxed for 2~10 h. Diluted with water, extracted by ethyl acetate, washed with brine, the organic phase was dried over anhydrous MgSO₄ and the filtrate was rotavapored in vacuo. The residue was further purified using flash column chromatography and eluting with petroleum ether and ethyl acetate or re-crystalized to afford the benzyl aryl ether product.

  4-(4'-Methoxybenzyloxy)phenyl acetate (1db): From p-(p-methoxybenzyloxy)phenol and acetic anhydride, yield 95%. White solid, m.p. 104~106 ℃; ¹H NMR (400 MHz, DMSO-d₆) δ: 7.41~7.35 (m, 2H), 7.05~6.98 (m, 4H), 6.97~6.92 (m, 2H), 5.00 (s, 2H), 3.75 (s, 3H), 2.23 (s, 3H); ¹³C NMR (101 MHz, DMSO-d₆) δ: 169.42, 158.99, 155.92, 155.47, 143.94, 129.46, 129.26, 128.81, 128.67, 122.53, 115.28, 114.92, 113.80, 69.29, 55.05, 20.74.

  Ethyl  2-(4-(4'-methoxybenzyloxy)phenoxy)acetate (1eb): From p-(p-methoxybenzyloxy)phenol and ethyl chloroacetate, yield 81%. White solid, m.p. 84~86 ℃; ¹H NMR (400 MHz, DMSO-d₆) δ: 7.37~7.33 (m, 2H), 6.95~6.89 (m, 4H), 6.87~6.82 (m, 2H), 4.94 (s, 2H), 4.68 (s, 2H), 4.15 (q, J＝7.1 Hz, 2H), 3.75 (s, 3H), 1.20 (t, J＝7.1 Hz, 3H); ¹³C NMR (101 MHz, CDCl₃) δ: 169.19, 159.46, 153.83, 152.24, 129.20, 115.89, 114.00, 70.44, 66.40, 61.27, 55.30, 14.17.

  1-Methoxy-4-((4'-(trifluoromethyl)phenoxy)methyl)ben-zene (1hb): From 4-(trifluoromethyl)phenol and p-me- thoxybenzyl chloride, yield 50%. White solid, m.p. 131~134 ℃; ¹H NMR (400 MHz, DMSO-d₆) δ: 7.65 (d, J＝8.7 Hz, 2H), 7.42~7.37 (m, 2H), 7.18 (d, J＝8.6 Hz, 2H), 6.98~6.93 (m, 2H), 5.11 (s, 2H), 3.76 (s, 3H); ¹³C NMR (101 MHz, DMSO-d₆) δ: 161.21, 159.12, 129.60, 128.21, 126.92, 126.88, 126.85, 126.81, 125.88, 123.19, 121.28, 120.96, 120.64, 115.27, 113.85, 69.31, 55.07.

  1-(2'-Methoxybenzyloxy)-4-methoxybenzene (1ad): From 4-methoxyphenol and 2-methoxybenzyl bromide, yield 82%. Colorless liquid. ¹H NMR (400 MHz, DMSO-d₆) δ: 7.39~7.29 (m, 2H), 7.04 (d, J＝7.8 Hz, 1H), 6.97~6.89 (m, 3H), 6.87~6.83 (m, 2H), 4.98 (s, 2H), 3.82 (s, 3H), 3.69 (s, 3H); ¹³C NMR (101 MHz, DMSO-d₆) δ: 156.79, 153.38, 152.50, 129.15, 128.85, 124.94, 120.22, 115.50, 114.57, 110.79, 64.94, 55.37, 55.30.

  1-(3'-Nitrobenzyloxy)-4-methoxybenzene (1af): From 4-methoxyphenol and 3-nitrobenzyl bromide, yield 91%. Colorless liquid. ¹H NMR (400 MHz, DMSO-d₆) δ: 8.30~8.28 (m, 1H), 8.22~8.15 (m, 1H), 7.92~7.87 (m, 1H), 7.69 (t, J＝7.9 Hz, 1H), 7.00~6.95 (m, 2H), 6.90~6.85 (m, 2H), 5.20 (s, 2H), 3.69 (s, 3H).

  4-((4'-Methoxyphenoxy)methyl)benzonitrile (1ag): From 4-(chloromethyl)benzonitrile and 4-methoxyphenol, yield 94%. White solid, m.p. 88~89 ℃; ¹H NMR (300 MHz, DMSO-d₆) δ: 7.85 (d, J＝8.1 Hz, 2H), 7.62 (d, J＝8.1 Hz, 2H), 6.99~6.81 (m, 4H), 5.15 (s, 2H), 3.69 (s, 3H).

  2-((4'-Methoxyphenoxy)methyl)naphthalene (1ai): From 2-(chloromethyl)naphthalene and 4-methoxyphenol, yield 84%. White solid, m.p. 127~128 ℃; ¹H NMR (400 MHz, DMSO-d₆) δ: 7.97~7.90 (m, 4H), 7.57 (dd, J＝8.4, 1.6 Hz, 1H), 7.55~7.49 (m, 2H), 7.01~6.96 (m, 2H), 6.89~6.83 (m, 2H), 5.21 (s, 2H), 3.68 (s, 3H); ¹³C NMR (101 MHz, DMSO-d₆) δ: 153.50, 152.31, 135.01, 132.76, 132.48, 127.97, 127.73, 127.57, 126.26, 126.08, 126.03, 125.64, 115.83, 114.59, 69.81, 55.31.

  4.3   General procedure for the rearrangement or deprotection

  To the titled compound (1.0 mmol) in 2.0 mL of DCE or toluene, 200 mg of PPA was added at the indicated temperature. The reaction progress was monitored by TLC. After the reaction was completed, the reaction mixture was worked-up with saturated NaHCO₃ and extracted by ethyl acetate. The organic phase was dried over anhydrous Na₂SO₄ and then the filtrate was rotavapored in vacuo. The residue was further purified using flash column chromatography and eluting with petroleum ether and ethyl acetate to afford the titled product.

  2-Benzyl-4-methoxyphenol (2aa (o)):^{[11b, 12b]} Yield 62%. White solid, m.p. 104~105 ℃; ¹H NMR (DMSO-d₆) δ: 8.91 (s, 1H), 7.27~7.20 (m, 4H), 7.17~7.12 (m, 1H), 6.71 (d, J＝8.2 Hz, 1H), 6.63~6.58 (m, 2H), 3.83 (s, 2H), 3.61 (s, 3H); NOESY (DMSO-d₆): NOE between phenolic- OH and only one aromatic CH, NOE between CH₂ of PMB with one aromatic CH and weak NOE between phenolic- OH and CH₂ of PMB, NOE between OCH₃ with one or two aromatic CHs.

  3-Benzyl-4-methoxyphenol (2aa (m)):^[12b] Yield 7%, colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.82 (s, 1H), 7.29~7.23 (m, 2H), 7.19~7.14 (m, 3H), 6.77 (d, J＝8.7 Hz, 1H), 6.55 (dd, J＝3.0, 8.7 Hz, 1H), 6.48 (d, J＝3.0 Hz, 1H), 3.80 (s, 2H), 3.68 (s, 3H).

  2-(4'-Methoxybenzyl)-4-methoxyphenol (2ab):^[12b] Yield 60%, colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.86 (s, 1H), 7.15~7.11 (m, 2H), 6.84~6.79 (m, 2H), 6.72~6.67 (m, 1H), 6.61~6.55 (m, 2H), 3.75 (s, 2H), 3.70 (s, 3H), 3.61 (s, 3H). The signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (o) but not 2aa (m).

  2-Benzyl-phenol (2ba (o)):^[13b] Yield 60%, colorless liquid. ¹H NMR (DMSO-d₆) δ: 9.36 (s, 1H), 7.29~7.10 (m, 5H), 7.03~6.99 (m, 2H), 6.80 (dd, J＝1.1, 7.3 Hz, 1H), 6.70 (td, J＝1.1, 7.4 Hz, 1H), 3.85 (s, 2H).

  4-Benzyl-phenol (2ba (p)):^[13b] Yield 17%, colorless liquid. ¹H NMR (DMSO-d₆) δ: 9.17 (s, 1H), 7.31~7.12 (m, 5H), 7.03~6.97 (m, 2H), 6.69~6.63 (m, 2H), 3.80 (s, 2H).

  4-(4'-Methoxybenzyl)-phenol (2bb):^[14b] Yield 58%. White solid, m.p. 75~78 ℃; ¹H NMR (DMSO-d₆) δ: 9.15 (s, 1H), 7.11~7.06 (m, 2H), 6.99~6.94 (m, 2H), 6.85~6.80 (m, 2H), 6.67~6.62 (m, 2H), 3.73 (s, 2H), 3.70 (s, 3H).

  2-Benzyl-1, 4-hydroquinone (2ca):^[15c] Yield 59%. White solid, m.p. 122~123 ℃; ¹H NMR (DMSO-d₆) δ: 8.63 (s, 1H), 8.52 (s, 1H), 7.28~7.23 (m, 2H), 7.21~7.12 (m, 3H), 6.63~6.57 (m, 1H), 6.42~6.40 (m, 2H), 3.78 (s, 2H).

  2-(4'-Methoxybenzyl)-1, 4-hydroquinone (2cb):^[15c] Yield 48%. White solid, m.p. 133~135 ℃; ¹H NMR (DMSO- d₆) δ: 8.60 (s, 1H), 8.50 (s, 1H), 7.12~7.08 (m, 2H), 6.84~6.79 (m, 2H), 6.57 (t, J＝8 Hz, 1H), 6.40~6.34 (m, 2H), 3.70 (s, 5H).

  2-Benzyl-4-acetoxyphenol (2da): Yield 60%. White solid, m.p. 100~102 ℃; ¹H NMR (DMSO-d₆) δ: 9.51 (s, 1H), 7.29~7.19 (m, 4H), 7.19~7.13 (m, 1H), 6.80~6.74 (m, 3H), 3.84 (s, 2H), 2.18 (s, 3H). The signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (o) but not 2aa (m). ¹³C NMR (DMSO-d₆) δ: 169.5, 152.5, 142.5, 140.7, 128.7, 128.2, 125.8, 123.0, 120.0, 115.1, 35.0, 20.7; ESI-HRMS calcd for C₁₅H₁₄NaO₃ [M+Na]⁺ 265.0841, found 265.0797.

  2-(4'-Methoxybenzyl)-4-acetoxyphenol (2db): Yield 64%. White solid, m.p. 100~102 ℃; ¹H NMR (DMSO- d₆) δ: 9.45 (s, 1H), 7.15~7.11 (m, 2H), 6.85~6.80 (m, 2H), 6.79~6.72 (m, 2H), 6.69 (d, J＝2.6 Hz, 1H), 3.77 (s, 2H), 3.70 (s, 3H), 2.17 (s, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (o) but not 2aa (m); ¹³C NMR (DMSO-d₆) δ: 169.5, 157.4, 152.4, 142.5, 132.5, 129.7, 128.8, 122.8, 119.9, 115.1, 113.7, 54.9, 34.1, 20.7; ESI-HRMS calcd for C₁₆H₁₆NaO₄ [M+Na]⁺ 295.0946, found 295.0953.

  Ethyl  2-(3-benzyl-4-hydroxyphenoxy)acetate (2ea): Yield 75%. White solid, m.p. 89~90 ℃; ¹H NMR (DMSO-d₆) δ: 8.99 (s, 1H), 7.30~7.10 (m, 5H), 6.70 (d, J＝8.3 Hz, 1H), 6.65~6.55 (m, 2H), 4.57 (s, 2H), 4.11 (q, J＝7.1 Hz, 2H), 3.82 (s, 2H), 1.17 (t, J＝7.1 Hz, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (o) but not 2aa (m); ¹³C NMR (DMSO-d₆) δ: 169.0, 150.4, 149.3, 140.9, 128.8, 128.7, 128.3, 128.1, 125.7, 116.8, 115.3, 112.7, 65.3, 60.4, 35.3, 14.0; ESI- HRMS calcd for C₁₇H₁₈NaO₄ [M+Na]⁺ 309.1103, found 309.1090.

  Ethyl  2-(3-(4'-methoxybenzyl)-4-hydroxyphenoxy)ace- tate (2eb): Reaction temperature: 0 ℃, reaction time: 5.5 h; yield 59%. White solid, m.p. 123~125 ℃; ¹H NMR (DMSO-d₆) δ: 8.98 (s, 1H), 7.16~7.10 (m, 2H), 6.85~6.80 (m, 2H), 6.72~6.66 (m, 1H), 6.61~6.55 (m, 2H), 4.57 (s, 2H), 4.12 (q, J＝7.1 Hz, 2H), 3.75 (s, 2H), 3.71 (s, 3H), 1.18 (t, J＝7.1 Hz, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (o) but not 2aa (m); ¹³C NMR (DMSO-d₆) δ: 169.0, 157.4, 150.3, 149.2, 132.8, 129.6, 129.4, 128.8, 116.6, 115.3, 113.6, 112.5, 65.3, 60.4, 55.3, 54.9, 34.4, 14.0; HRMS (ESI) calcd for C₁₈H₂₀NaO₅ [M+Na]⁺ 339.1208, found 339.1202.

  Ethyl  3-benzyl-4-hydroxybenzoate (2fa):^[18b] Reaction temperature: 70 ℃, reaction time: 26 h; yield 68%. White solid, m.p. 137~139 ℃; ¹H NMR (DMSO-d₆) δ: 10.41 (s, 1H), 7.69~7.66 (m, 2H), 7.30~7.13 (m, 5H), 6.89 (d, J＝8.2 Hz, 1H), 4.21 (q, J＝7.1 Hz, 2H), 3.90 (s, 2H), 1.25 (t, J＝7.1 Hz, 3H); ¹³C NMR (DMSO-d₆) δ: 165.6, 159.6, 140.6, 131.7, 129.2, 128.6, 128.3, 127.7, 125.8, 120.5, 114.9, 60.0, 34.9, 14.2.

  Ethyl  3-(4'-methoxybenzyl)-4-hydroxybenzoate (2fba): Reaction temperature: 0 ℃, reaction time: 5 h; yield 11%. White solid, m.p. 120~122 ℃; ¹H NMR (DMSO-d₆) δ: 9.36 (s, 1H), 7.29~7.10 (m, 5H), 7.03~6.99(m, 2H), 6.81~6.79(m, 1H), 6.70 (td, J＝1.1, 7.4 Hz, 1H), 3.85 (s, 2H); ¹³C NMR (DMSO-d₆) δ: 165.6, 159.5, 157.4, 132.4, 131.5, 129.6, 129.1, 128.2, 120.4, 114.8, 113.7, 60.0, 54.9, 34.0, 14.2; ESI-HRMS calcd for C₁₇H₁₈NaO₄ [M+Na]⁺ 309.1103, found 309.1053.

  Ethyl  3, 5-bis(4'-methoxybenzyl)-4-hydroxybenzoate (2fbb): Reaction temperature: 0 ℃, reaction time: 5 h; yield 13%. White solid, m.p. 117~119 ℃; ¹H NMR (DMSO-d₆) δ: 9.17 (s, 1H), 7.31~7.12 (m, 5H), 7.03~6.97 (m, 2H), 6.69~6.63 (m, 2H), 3.80 (s, 2H); ¹³C NMR (DMSO-d₆) δ: 165.6, 159.5, 157.3, 155.1, 132.7, 132.1, 131.5, 130.5, 129.4, 129.1, 129.0, 128.1, 127.4, 120.4, 114.8, 113.5, 110.7, 60.0, 55.3, 54.9, 14.2; HRMS (ESI) calcd for C₂₅H₂₆O₅Na [M+Na]⁺ 429.1678, found 429.1674.

  2-Benzyl-4-cyano-phenol (2ga): Reaction temperature: 70 ℃, reaction time: 46 h; yield 39%. White solid, m.p. 126~127 ℃; ¹H NMR (DMSO-d₆) δ: 10.74 (s, 1H), 7.52~7.49 (m, 2H), 7.30~7.15 (m, 5H), 6.96~6.91 (m, 1H), 3.87 (s, 2H); ¹³C NMR (DMSO-d₆) δ: 159.4, 140.0, 134.2, 132.1, 129.2, 128.6, 128.3, 126.0, 119.6, 115.9, 100.9, 34.7; HRMS (ESI) calcd for C₁₄H₁₁NNaO [M+ Na]⁺ 232.0738, found 232.0731.

  2-Methoxy-4-nitro-6-benzyl-phenol (2ja): Reaction temperature: 70 ℃, reaction time: 10 h; yield 20%. Yellow semi-solid; ¹H NMR (DMSO-d₆) δ: 10.39 (s, 1H), 7.71 (d, J＝2.6 Hz, 1H), 7.67 (d, J＝2.7 Hz, 1H), 7.31~7.16 (m, 5H), 3.97 (s, 2H), 3.92 (s, 3H); ¹³C NMR (DMSO-d₆) δ: 151.0, 147.1, 139.8, 139.0, 128.7, 128.4, 128.0, 126.1, 118.7, 105.1, 56.3, 34.8; HRMS (ESI) calcd for C₁₄H₁₄NO₄ [M+H]⁺ 260.0923, found 260.0918.

  2-Methoxy-4-formyl-6-benzyl-phenol (2ka):^[23b] Reaction temperature: 25 ℃, reaction time: 14 h; yield 45%, m.p. 89~91 ℃; ¹H NMR (DMSO-d₆) δ: 10.50~9.70 (br s, 1H), 9.73 (s, 1H), 7.33~7.32 (m, 2H), 7.30~7.13 (m, 5H), 3.94 (s, 2H), 3.87 (s, 3H).

  2-Methoxy-6-benzyl-phenol (2la (o)):^[24b] Reaction temperature: 70 ℃, reaction time: 6 h; yield 22%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 9.26 (s, 1H), 7.27~7.13 (m, 5H), 6.81 (t, J＝8.0 Hz, 1H), 6.71 (dd, J＝2.0, 8.0 Hz, 1H), 6.58 (dd, J＝2.0, 8.0 Hz, 1H), 3.87 (s, 2H), 3.62 (s, 3H).

  2-Methoxy-5-benzyl-phenol (2la (m)):^[24c] Reaction temperature: 70 ℃, reaction time: 6 h; yield 47%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.53 (s, 1H), 7.26~7.19 (m, 5H), 6.81 (dd, J＝2.0, 4.0 Hz, 1H), 6.70~6.64 (m, 2H), 3.87 (s, 2H), 3.77 (s, 3H).

  2-Benzyl-3-methoxy-phenol (2ma (o)):^[25a] Reaction temperature: 50 ℃, reaction time: 22 h; yield 20%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 9.36 (s, 1H), 7.22~7.16 (m, 4H), 7.13~7.06 (m, 1H), 6.98 (t, J＝8.2 Hz, 1H), 6.48 (d, J＝10.1 Hz, 1H), 6.45 (d, J＝10.1 Hz, 1H), 3.85 (s, 2H), 3.72 (s, 3H). Product 2ma (o) has the identical ¹H NMR signal pattern of 3 aromatic C—Hs of phenolic moiety to the literature ^[25a].

  3-Methoxy-6-benzyl-phenol (2ma (o')):^[25b] Reaction temperature: 50 ℃, reaction time: 22 h; yield 35%. Semi-solid. ¹H NMR (DMSO-d₆) δ: 9.40 (s, 1H), 7.26~7.10 (m, 5H), 6.92 (d, J＝8.3 Hz, 1H), 6.38 (s, 1H), 6.31 (dd, J＝2.5, 8.3 Hz, 1H), 3.78 (s, 2H), 3.65 (s, 3H).

  2-Benzyl-6-methyl-phenol (2na (o)):^[26b] Reaction temperature: 15 ℃, reaction time: 15 h; yield 60%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.33 (s, 1H), 7.27~7.12 (m, 5H), 6.92 (d, J＝7.4 Hz, 1H), 6.89~6.84 (m, 1H), 6.66 (t, J＝7.4 Hz, 1H), 3.90 (s, 2H), 2.16 (s, 3H).

  4-Benzyl-6-methyl-phenol (2na (p)):^[26c] Reaction temperature: 50 ℃, reaction time: 15 h; yield 23%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 9.02 (s, 1H), 7.32~7.22 (m, 2H), 7.21~7.09 (m, 3H), 6.89 (s, 1H), 6.82 (d, J＝8.1 Hz, 1H), 6.67 (d, J＝8.1 Hz, 1H), 3.77 (s, 2H), 2.06 (s, 3H).

  2-Benzyl-1-naphthol (2oa):^[27] Reaction temperature: 25 ℃, reaction time: 19 h; yield 65% (based on 44% reacted compound 1oa). White solid, m.p. 71~73 ℃; ¹H NMR (DMSO-d₆) δ: 9.28 (s, 1H), 8.24~8.19 (m, 1H), 7.81~7.76 (m, 1H), 7.47~7.40 (m, 2H), 7.35 (d, J＝8.3 Hz, 1H), 7.27~7.22 (m, 5H), 7.19~7.12 (m, 1H), 4.13 (s, 2H).

  2-(4'-Methoxybenzyl)-1-naphthol (2ob (o)):^{[27, 28b]} Reaction temperature: 25 ℃, reaction time: 8 h; yield 38%. White solid, m.p. 80~82 ℃; ¹H NMR (DMSO-d₆) δ: 9.25 (s, 1H), 8.22 (dd, J＝1.2, 7.9 Hz, 1H), 7.77 (dd, J＝2.0, 7.3 Hz, 1H), 7.47~7.39 (m, 2H), 7.34 (d, J＝8.3 Hz, 1H), 7.21 (d, J＝8.4 Hz, 1H), 7.19~7.14 (m, 2H), 6.85~6.80 (m, 2H), 4.07 (s, 2H), 3.69 (s, 3H).

  4-(4'-Methoxybenzyl)-1-naphthol (2ob (p)): Reaction temperature: 25 ℃, reaction time: 8 h; yield 30%, Yellow liquid. ¹H NMR (DMSO-d₆) δ: 9.98 (s, 1H), 8.18~8.11 (m, 1H), 7.90 (dd, J＝2.1, 7.2 Hz, 1H), 7.45~7.38 (m, 2H), 7.17~7.08 (m, 3H), 6.82~6.78 (m, 3H), 4.21 (s, 2H), 3.68 (s, 3H); ¹³C NMR (DMSO-d₆) δ: 157.3, 152.0, 133.2, 132.4, 129.3, 127.4, 127.2, 126.0, 125.0, 124.2, 124.1, 122.5, 113.6, 107.4, 54.9, 36.9; ESI-HRMS calcd for C₁₈H₁₅O₂ [M－H]^－ 263.1072, found 263.1079.

  2-Benzyl-1-naphthol (2pa):^[29b] Reaction temperature:100 ℃ (in toluene); reaction time: 48 h; yield 47%. White solid, m.p. 92~94 ℃; ¹H NMR (DMSO-d₆) δ: 9.60 (br s, 1H), 7.85 (d, J＝8.0 Hz, 1H), 7.78 (d, J＝8.0 Hz, 1H), 7.70 (d, J＝8.0 Hz, 1H), 7.50~7.30 (m, 1H), 7.15~7.30 (m, 6H), 7.12~7.05 (m, 1H), 4.35 (s, 2H).

  2-(4'-Methoxybenzyl)-1-naphthol (2pb):^[29b] Reaction temperature: 15 ℃, reaction time: 8 h; yield 58%. White solid, m.p. 118~119 ℃; ¹H NMR (DMSO-d₆) δ: 9.71 (s, 1H), 7.84 (d, J＝8.5 Hz, 1H), 7.76 (d, J＝8.0 Hz, 1H), 7.68 (d, J＝8.8 Hz, 1H), 7.39~7.33 (m, 1H), 7.25~7.21 (m, 2H), 7.12 (d, J＝8.6 Hz, 2H), 6.76 (d, J＝8.6 Hz, 2H), 4.26 (s, 2H), 3.65 (s, 3H).

  2-Allyl-4-methoxyphenol (2ac):^[30b] Reaction temperature: 20 ℃, reaction time: 17 h; yield 39%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.82 (s, 1H), 6.72~6.67 (m, 1H), 6.62~6.56 (m, 2H), 5.98~5.88 (m, 1H), 5.07~4.96 (m, 2H), 3.64 (s, 3H), 3.25~3.24 (m, 2H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is identical to the reference^[37b] and similar to 2aa (o) but not 2aa (m).

  3-(2'-Methoxybenzyl)-4-methoxyphenol (2ad): Reaction temperature: 20 ℃, reaction time: 8 h; yield 76%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.84 (s, 1H), 7.18 (td, J＝8.2, 1.7 Hz, 1H), 6.98~6.93 (m, 2H), 6.83 (td, J＝0.8, 7.3 Hz, 1H), 6.71 (d, J＝8.7 Hz, 1H), 6.59 (dd, J＝8.7, 3.1 Hz, 1H), 6.45 (d, J＝3.1 Hz, 1H), 3.78 (s, 3H), 3.77 (s, 2H), 3.58 (s, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (m) but not 2aa (o); ¹³C NMR (DMSO-d₆) δ: 157.0, 152.0, 149.0, 129.7, 128.4, 127.5, 127.1, 120.1, 116.0, 115.2, 111.4, 110.5, 55.2, 55.10, 29.4; ESI-HRMS calcd for C₁₅H₁₇O₃ [M+H]⁺ 245.1178, found 245.1166.

  4-Methoxy-3-(naphthalen-2'-ylmethyl)phenol (2ai): Reaction temperature: 25 ℃, reaction time: 12 h; yield 59%. White solid, m.p. 89~90 ℃; ¹H NMR (DMSO-d₆) δ: 8.95 (s, 1H), 7.86~7.78 (m, 3H), 7.69 (s, 1H), 7.48~7.39 (m, 3H), 6.73 (d, J＝8.7 Hz, 1H), 6.68 (d, J＝3.0 Hz, 1H), 6.62 (dd, J＝8.7, 3.1 Hz, 1H), 4.00 (s, 2H), 3.61 (s, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (m) but not 2aa (o); ¹³C NMR (DMSO-d₆) δ: 152.1, 148.8, 138.8, 133.1, 131.5, 128.1, 127.7, 127.6, 127.4, 127.3, 126.4, 125.9, 125.2, 116.2, 115.5, 111.9, 55.2, 35.6; ESI-HRMS calcd for C₁₈H₁₆NaO₂ [M+Na]⁺287.1048, found 287.1060.

  4-Methoxy-3-(naphthalen-1'-ylmethyl)phenol (2aj): Reaction temperature: 70 ℃, reaction time: 6 h; yield 70%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 9.12 (s, 1H), 8.09~8.03 (m, 1H), 7.94~7.90 (m, 1H), 7.80 (d, J＝8.1 Hz, 1H), 7.52~7.47 (m, 2H), 7.46~7.42 (m, 1H), 7.29 (d, J＝6.8 Hz, 1H), 6.78 (d, J＝8.7 Hz, 1H), 6.61 (dd, J＝3.1, 8.7Hz, 1H), 6.36 (d, J＝3.1 Hz, 1H), 4.28 (s, 2H), 3.51 (s, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (m) but not 2aa (o); ¹³C NMR (DMSO-d₆) δ: 152.0, 148.6, 136.8, 133.4, 131.6, 128.4, 127.5, 126.7, 126.6, 125.9, 125.6, 125.6, 124.1, 116.0, 115.4, 111.4, 55.0, 31.9; HRMS (ESI) calcd for C₁₈H₁₆NaO₂ [M+Na]⁺ 287.1048, found 287.1041.

  4-Methoxy-2-(1'-phenylethyl)phenol (2ak (o)):^[33b] Reaction temperature: 25 ℃, reaction time: 22 h; yield 25%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.80 (s, 1H), 7.29~7.12 (m, 5H), 6.76~6.74 (m, 1H), 6.54~6.52 (m, 2H), 4.42 (q, J＝7.2 Hz, 1H), 3.65 (s, 3H), 1.46 (d, J＝7.3 Hz, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (o) but not 2aa (m). Product 2ak (o) has the identical ¹H NMR signal pattern of 3 aromatic C—Hs of phenolic moiety to the literature ^[33b].

  4-Methoxy-3-(1'-phenylethyl)phenol (2ak (m)): Reaction temperature: 25 ℃, reaction time: 22 h; yield 45%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.87 (s, 1H), 7.28~7.22 (m, 4H), 7.17~7.13 m, 1H), 6.68 (d, J＝8.6 Hz, 1H), 6.64 (d, J＝3.0 Hz, 1H), 6.58 (dd, J＝3.1, 8.6 Hz, 1H), 4.42 (q, J＝7.3 Hz, 1H), 3.62 (s, 3H), 1.49 (d, J＝7.3 Hz, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (m) but not 2aa (o); ¹³C NMR (DMSO-d₆) δ: 152.1, 148.2, 146.1, 133.3, 128.0, 127.4, 125.6, 115.3, 113.6, 111.0, 55.2, 37.0, 20.5; HRMS (ESI) calcd for C₁₅H₁₆NaO₂ [M+Na]⁺ 251.1048, found 251.1041.

  3-Benzhydryl-4-methoxyphenol (2ala):^[34b] Reaction temperature: 15 ℃, reaction time: 24 h; yield 16%. Colorless liquid. ¹H NMR (DMSO-d₆) δ: 8.99 (s, 1H), 7.30~7.26 (m, 4H), 7.21~7.17 (m, 2H), 7.10~6.96 (m, 4H), 6.73 (d, J＝8.0 Hz, 1H), 6.65 (dd, J＝4.0, 8.0 Hz, 1H), 6.25 (d, J＝4.0 Hz, 1H), 5.77 (s, 1H), 3.55 (s, 3H), the signal pattern of 3 aromatic C—Hs of phenolic moiety is similar to 2aa (m) but not 2aa (o).

  3, 5-Dibenzhydryl-4-methoxyphenol (2alb): Reaction temperature: 15 ℃, reaction time: 24 h; yield 23%. White solid, m.p. 146~148 ℃; ¹H NMR (DMSO-d₆) δ: 8.88 (s, 1H), 7.31~7.27 (m, 8H), 7.21~7.17 (m, 4H), 7.10~7.08 (m, 4H), 7.04~7.02 (m, 4H), 6.38 (d, J＝4.0 Hz, 2H), 5.74 (s, 2H); ¹³C NMR (DMSO-d₆) δ: 149.1, 148.1, 143.6, 143.6, 130.7, 129.0, 129.0, 128.4, 128.2, 128.2, 126.0, 126.0, 116.9, 113.4, 56.0, 49.3, 48.7; HRMS (ESI) calcd for C₃₃H₂₈NaO₂ [M+Na]⁺ 479.1987, found 479.1980.

  Supporting Information   Structures of bioactive diarylmethanes; Structures of bioactive benzylated phenols; Structures of NOE effect in compound 1aa (o); ¹H NMR and ¹³C NMR spectra of benzyl aryl ether compounds 1db, 1eb, 1hb, 1ad, 1af, 1ag, 1ai; ¹H NMR and ¹³C NMR spectra of the rearranged products. The Supporting Information is available free of charge via the Internet at http://sioc-journal.cn/.

  
  
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  Scheme 1  Synthesis of 1aa to 1al and reaction process of benzyl rearrangement

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  Table 1.  Influence of catalysts and solvents on the benzyl rearrangement at 25 ℃

  Entry	Catalyst	Solventa	Time/h	Ratiob/%
  				2aa (o)c	2aa (m)d	3a	Unreacted 1aa
  1e	PPA	DCE	72	62	7	Trace	Trace
  2	PPA	Dry DCM	180	60	10	10	20
  3	H3PO4 (≥85%)	DCE	60	NR	NR	NR	100
  4	PPTS	DCE	60	NR	NR	NR	100
  5	TsOH•H2O	DCE	60	NR	NR	NR	100
  6	TFA	DCE	126	40	10	30	10
  7	Cond. HCl	DCE	40	NR	NR	NR	100
  8	Cond. HCl	Dry DCM	80	NR	NR	NR	100
  9	Anhydrous AlCl3	Dry DCM	10	40	Trace	30	0
  10	Anhydrous ZnCl2	Dry DCM	168	NR	NR	Trace	> 95
  11e	PPA	Toluene	96	65	20	10	Trace
  12	PPA	THF	96	NR	NR	NR	100
  13	PPA	Dioxane	120	—	—	Trace	> 95
  14	PPA	DME	124	—	—	Trace	80
  15	PPA	Ethyl ether	96	NR	NR	NR	100
  a The solvent was used directly or treated for anhydrous goal before use. Asterisk (*) denotes minor regioisomer. b The ratio was estimated by TLC except Entries 1 and 11. —, NR, and trace represent not detectable, no reaction and lower than 5%, respectively. c ortho to hydroxy. d meta to hydroxy. e Isolated yields.

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  Table 2.  Effects of EWG and EDG substitutions at phenolic moiety on the rearrangement^a

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  Table 3.  Influences of combined substitutions, substitution positions and varied arenes at phenolic moiety on the rearrangement^a

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  Table 4.  Effects of benzyl groups or benzyl-like groups on the rearrangement^a

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