Racemic-1,1 -binaphthyl-2,2 -diol

Keywords Aryl iodides, aliphatic amines, CuBr, racemic-1,1 -binaphthyl-2,2 -diol (rac-BINOL), K3PO4, N,N-Dimethyl formamide (DMF), room temperature, coupling reaction, amination, N-arylation of aliphatic amines... 

Diols such as the optically active 1,1 -binaphthyl-2-2 -diol (BINOL) have been used as versatile templates and chiral auxiliaries in catalysts employed successfully in asymmetric synthesis. The application of enzymes in the enantioselective access to axially dissymmetric compounds was first reported by Fujimoto and coworkers.83 In aqueous media, the asymmetric hydrolysis of the racemic binaphthyl dibutyrate (the ester) using whole cells from bacteria species afforded the (A)-diol with 96%ee and the unreacted substrate (A)-ester with 94% ee at 50 % conversion. Recently, in non-aqueous media, lipases from Pseudomonas cepacia and Ps. fluorescens have been employed in the enantioselective resolution and desymmetrization of racemic 6,6 -disubstituted BINOL derivatives using vinyl acetate.84 The monoacetate (K)-73 (product) was obtained in 32-44 % chemical yields and 78-96% ee depending on the derivatives used. The unreacted BINOL (S)-72 was obtained in 30-52 % chemical yield and 55-80% ee. 

Optically active diols have been used for several asymmetric syntheses [67] and chiral resolutions [68]. In 1990, Kawashima and co-workers [69] reported the first example of direct optical resolution of racemic 2,2 -dihydroxy-l,l -binaphthyl (34) with (R,R)-29. In this procedure equimolar amounts of racemic 34 and (R,R)-29 were added in benzene and the mixture was heated to a homogeneous solution and then cooled to room temperature. After crystallization of the precipitate and treatment with hydrochloric acid, (R)-(+)-34 was obtained with an optical purity of 94% and in a yield of 86% based on the amount of enantiomer presents in the racemate (Scheme 23). 

The 1,1-binaphthyl ring system is a key component of a number of chiral ligands that have been used as catalysts for asymmetric synthesis <1992S503>. Chemo- and stereoselective (. )-stannepin-catalyzed monobenzoylation of terminal 1,2-diols 312 afforded ( -enantiomer-enriched 2-benzoylated diols 313 in moderate selectivity. Only a trace of 1-benzoylated diols 314 was observed (Equation 55). Thus, the method was successfully applied to kinetic resolution of racemic 1-phenyl-1,2-ethanol using a chiral organotin catalyst <2000JOC996>. 

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