A Mild and Convenient Method for the Synthesis ofSubstituted BINOL

YANG Huameng, YE Fei, JIANG Jianxiong, LAI Guoqiao,ZHENG Zhanjiang

(Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University,Hangzhou 310012, China)

A Mild and Convenient Method for the Synthesis ofSubstituted BINOL

YANG Huameng, YE Fei, JIANG Jianxiong, LAI Guoqiao,ZHENG Zhanjiang

(Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University,Hangzhou 310012, China)

An efficient and mild method for the synthesis of substituted BINOL was developed by the oxidative coupling of 2-naphthol of the method used 5 mol% CuCl and 1.5 mol% amino-functional polysiloxanes(AFP), which could provide a variety of substituted BINOL effectively. The coupling reaction could be performed at room temperature.

oxidative coupling; amino-functional polysiloxane; BINOL

1 Introduction

The most important application of polymers as a supporter in synthetic chemistry is the use of cross-linked polymers (insoluble polymers) in solid phase and combinational synthesis, and soluble polymers did not receive so much attention for use as supports. However, the use of a soluble polymer support offers advantages of homogeneity during synthesis and during characterization[1], so that it is necessary to develop strategy that use soluble polymers as supports and polymer catalysts. Untill now, Polystyrene (linear), Poly(ethylene glycol) (PEG) etc. were used[2-8]. Polysiloxanes, common and commercially available, are soluble polymers and should be studied intensively, but only few reports described the use of Polysiloxanes support ligand[9].

1,1’-Bi-2-naphthol(BINOL) and its derivatives have received intense attention due to widely applications of their enantiomers as chiral inducers in synthetic chemistry, and a number of methods have been developed for their preparation by the oxidative coupling of naphthols. For example, Fe, Mn, Cu, Ti and Ru Salts were used in stoichiometric amount to mediate the coupling[10-14]. Whereas CuCl2-amine/AgCl, CuCl(OH)TMEDA/O2, CuSO4(Al2O3)/ O2, VO(acac)2, and FeCl3in the presence of ultra-sound irradiation were employed as catalytic systems to assist the oxidative coupling[15-19]. However, most of these methods suffer from drawbacks such as the production of stoichiometric amounts of metal waste, the need for high temperatures and the need for long reaction times. We report here a simple and convenient method for the oxidative coupling of 2-naphthols in the presence of CuCl and Amino-Functional Polysiloxanes (AFP).

Scheme 1 Commercial available amino-functional polysiloxanes

2 Results and Discussions

Initially, in a model experiment, a mixture of 2-naphthol and CuCl were stirred in CH2Cl2at room temperature, unfortunately, there’s no product detected. But, when 1.5 mol% of amino functional polysiloxane (AFP) was added as ligand, the reaction proceeded efficiently at room temperature, and BINOL was obtained in 85% yield. Then, different solvents were tested in this coupling reaction. As shown inTable1, Toluene, CH2Cl2, CHCl3and CH2ClCH2Cl provided excellent results, and among them, 1,2-dichloroethane was the most efficient (92%). Consequently,1,2-dichloroethane was choosen as the solvent for subsequent experiments. In the next step, the effects of different copper salts on the coupling reaction have been investigated. As shown inTable2, CuCl proved to be the best catalyst, while when CuI, CuBr were used, the yields were relatively low. Cu(II) salts, CuCl2, CuBr2, CuI2, CuF2, Cu(OTf)2, Cu(CF3COO)2·XH2O also demonstrated poor activity. Only Cu2O giving a moderate yield. Therefore, the optimized condition for the coupling reaction of 2-naphthol is using 5 mol% of CuCl as catalyst in 1,2-Dichloroethane in the presence of 1.5 mol% of AFP.

Several 2-Naphthols have been employed for this coupling reaction according to the optimized condition. As shown inTable3, when 6-MeO-2-Naphthol, 7-MeO-2-Naphthol, 6-Br-2-Naphthol and 6-CN-2-Naphthol were used, the desired product were obtained in good yield, while when 6-COOMe was used, the yield diminished to 63%.

3 Conclusions

In conclusion, we have demonstrated an efficientand mild process for the synthesis of substituted BINOL by the oxidative coupling of 2-naphthol. Using 5 mol% Cu salt, in the presence of 1.5 mol% amino-functional polysiloxanes (AFP) as ligand, the desired products were obtained in good yields. The method is very simple, mild, and applicable to various substrates.

Tab. 1 Effect of various solvents on the coupling of 2-naphthol

aAll the reaction were performed at room temperature.

bIsolated yield.

Tab. 2Effectofcoppersaltsonthecouplingof2-naphthol

EntryCu/5mol%t/hYield/%b1CuCl36822CuI48trace3CuBr48194Cu2O48475CuCl248236CuBr248trace7CuI248trace8CuF248139Cu(OTf)2481310Cu(CF3COO)2·XH2O48trace

aAll the reaction were performed at room temperature.

bIsolated yield.

Tab. 3Thecoupingreactionofsubstituted2-naphthol

EntryRt/hYield/%b16⁃OCH3362a：7627⁃OCH3362b：7336⁃Br362c：8246⁃CN362d：8956⁃COOMe362e：63

aAll the reaction were performed at room temperature.
bIsolated yield

4 Experimental

All reaction flask and solvent were dried according to standard method prior to use. Amino-functional Polysiloxane (AFP) was purchased from Hangzhou Bald Silicone Co., Ltd. (0.21 mmol /g polysiloxane, Mw ～2200), IR (cm-1): 2962, 2905, 1412, 1261, 1093, 864, 800; GPC: Mw: 2200, Mw/Mn=2.18; Gel permeation chromatographic analysis (GPC) measurements were conducted on waters GPC, Flash column chromatography was performed over silica (100-200 mesh). NMR spectra were recorded on a 400 MHz spectrometer (Avance 400).13C NMR spectra were obtained with broadband proton decoupling. For spectra recorded in CDCl3or d-DMSO, unless noted, chemical shifts were recorded relative to the internal TMS (tetramethylsilane) reference signal. GC-MS was performed on a TRACE DSQ.Thin layer chromatography was performed using Silica.

GeneralprocedureforthepreparationofsubstitutedBINOL

A mixture of substituted naphthol (0.4 mmol), amino-functional polysiloxane 1d(0.219 mmol/g, 0.12 mmol), Cu salt (5 mmol%) and 1,2-Dichloroethane (1 mL) in a 10 mL flask was stirred at rt for 36 h. Then CH2Cl2(5 mL) was added to extract for 3 times. The extracted liquids were washed with water (10 mL×3) and brine (10 mL×3), then dried with Na2SO4,concentrated in vacuo, and purified by column chromatography on silica gel (EtOAc-petro ether, 1∶6) to gain the pure product. The spectral data of all compounds matched in all respects with reported data[20].

2a: 6,6′-Bimethoxy-1,1′-binaphthyl-2,2′-diol

1H-NMR (400 MHz, CDCl3): δ (ppm) = 7.86 (d,J= 8.8 Hz, 2 H), 7.36 (d,J= 8.4 Hz, 2 H), 7.23 (s, 2 H), 7.08 (d,J= 9.2 Hz, 2 H), 5.00 (s, 2 H), 3.92 (s, 6 H). MS (EI):m/z=346.10 (C22H18O4).

2b: 7,7′-Bimethoxy-1,1′-binaphthyl-2,2′-diol

1H-NMR (400 Mz, CDCl3): δ (ppm) = 7.89 (d,J= 8.4 Hz, 2 H), 7.80 (d,J= 8.4 Hz, 2 H), 7.24 (d,J= 8.4 Hz, 2 H), 7.06 (d,J= 8.8 Hz, 2 H), 6.51 (s, 2 H), 5.10 (s, 2 H), 3.59 (s, 6 H). MS (EI):m/z=346.12 (C22H18O4).

2c: 6,6′-Dibromo-1,1′-binaphthyl-2,2′-diol

1H-NMR (400 MHz, CDCl3): δ (ppm) = 8.03 (s, 2 H), 7.90 (d,J= 8.4 Hz, 2 H), 7.40 (m, 4 H), 6.98 (d,J= 8.8 Hz, 2 H), 5.12 (br, 2 H). MS (EI):m/z=443.91 (C20H12Br2O2).

2d: 6, 6′-Dicyano-1,1′-binaphthyl-2, 2′-diol

1H-NMR (400 MHz, CDCl3): δ (ppm) = 8.07 (s, 2 H), 7.66 (m, 4 H), 7.48 (s, 2 H), 7.11 (s, 2 H), 5.67 (br, 2 H). MS (EI):m/z=336.09 (C22H12N2O2).

2e: 6, 6′-Bismethoxycarbonyl-1,1′-binaphthyl-2, 2′-diol

1H-NMR (400 MHz, d-DMSO): δ (ppm) = 8.49 (s, 2 H), 7.97 (d,J= 8.4 Hz, 2 H), 7.86 (d,J= 8.8 Hz, 2 H), 7.76 (d,J= 8.8 Hz, 2 H), 7.18 (s, 2 H), 3.87 (s, 6H). MS (EI):m/z=402.11 (C24H18O6).

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一种温和方便的合成取代联萘酚的方法

杨化萌，叶 飞，蒋健雄，来国桥，郑战江

(杭州师范大学有机硅化学及材料技术教育部重点实验室，浙江 杭州 310012)

发展了一种高效温和的用2-萘酚氧化偶联合成取代的联萘酚的方法，采用5 mol% CuCl, 1.5 mol%的氨基聚硅氧烷，可以高收率地得到各种取代的联萘酚.这个反应可以在室温下进行.

氧化偶联；氨基聚硅氧烷；联萘酚

date：2012-12-01

Supported by Qianjiang Talents Project( 2010R0017).

ZHENG Zhanjiang(1978—)，male，Research Associate，Ph.D.，majored in organic synthesis and catalysis.E-mail:zzjiang78@hotmail.com

10.3969/j.issn.1674-232X.2013.01.005

O625.1ArticlecharacterA

1674-232X(2013)01-0026-04