Optical resolution of diols

Optical Resolution of Diols with Chiral Diamines... 

Mori, K., and Toda, F. (1990) Optical Resolution of Arsine Oxides by Complexation with Optically Active [1,1 -Binaphthyl]-2,2 -diol, Bull. Chem. Soc. Jpn., 63, 2127-2128. 

Toda, F., Tanaka, K., Stein, Z., and Goldberg, I. (1994) Optical Resolution of Binaphthol and Biphenanthryl Diols by Inclusion Crystallization with V-Alkyl- cinchonidinium Halides. Structural Characterization of the Resolved Materials, J. Org. Chem., 59, 5748-5751. 

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). 

Enzymatic resolution has been successfully applied to the preparation of optically active gem-difluorocyclopropanes (see Scheme 12.4). We succeeded in the first optical resolution of racemic gm-difluorocyclopropane diacetate, trans-43, through lipase-catalyzed enantiomer-specific hydrolysis to give (R,R)-(-)-44 with >99% ee (see equation 9, Scheme 12.4) [4a], We also applied lipase-catalyzed optical resolution to an efficient preparation of monoacetate cw-46 from prochiral diacetate m-45 (see equation 10, Scheme 12.4) [4a], Kirihara et al. reported the successful desymmetrization of diacetate 47 by lipase-catalyzed enantiomer-selective hydrolysis to afford monoacetate (R)-48, which was further transformed to enantiopure amino acid 15 (see equation 11, Scheme 12.4) [19]. We demonstrated that the lipase-catalyzed enantiomer-specific hydrolysis was useful for bis-gem-difluorocyclopropane 49. Thus, optically pure diacetate (R,S,S,R)-49 and (S,R,R,S)-diol 50, were obtained in good yields, while meso-49 was converted to the single monoacetate enantiomer (R,S,R,S)-51 via efficient desymmetrization (see equation 12, Scheme 12.4) [4b, 4e], Since these mono- and bis-gm-difluorocyclopropanes have two hydroxymethyl groups to modify, a variety of compounds can be prepared using them as building blocks [4, 22],... 

ABSTRACT. Novel optical resolutions of guest compounds by inclusion complex formation with optically active host compound are reviewed Tertiary acetylenic alcohols, cyanohydrins, and secondary alcohols were resolved by complexation with alkaloids such as brucine or sparteine. Cycloalkanones, 2,3 -epoxycyclohexanones, and some other neutral compounds were resolved by complex formation with optically active diacetylenic diol. Mutual optical resolution of bis-g-naphthol and sulfoxides by complex formation was also reviewed. 

Previously, we have reported a high ability of 1,1,6,6-tetra-phenylhexa-2,4-diyne-l,6-diol ( ) to include various guest compounds. When this diacetylenic diol is optically active, it can be used for an optical resolution of the guest compound. Optically active diacetylenic diol can easily be... 

Optical Resolution of 3-Methylcycloalkanones and 5-Methyl-y -butyrolactone by Complexation with Optically Active 1,6-Bis(o-chlorophenyl)-1,6-diphenylhexa-2,4-diyne-l,6-diol... 

Optical resolution methods with carane-3,4-diol are noteworthy for wide generality. Esters of various cyclopropane carboxylic acids with (1,S, 3A>,4A>,6A>)-carane-3,4-diol were prepared and all (lR)-isomers could easily be obtained by a simple silica gel column chromatography. 

Resolution of bicyclic enones. This optically active diol selectively forms a hydrogen-bonded insoluble complex with one enantiomer of the bicyclic enone 2, which when heated liberates ( — )-2 of 100% ee. This resolution is useful for a few... 

Recently, Schaumann et al. 153,154 an(j Bienz et tf/.155,156 have developed dependable routes for the resolution of racemic functionalized organosilanes with Si-centered chirality using chiral auxiliaries, such as binaphthol (BINOL), 2-aminobutanol, and phenylethane-l,2-diol (Scheme 2). For instance, the successive reaction of BINOL with butyllithium and the chiral triorganochlorosilanes RPhMeSiCl (R = /-Pr, -Bu, /-Bu) affords the BINOL monosilyl ethers 9-11, which can be resolved into the pure enantiomers (A)-9-ll and (7 )-9-11, respectively. Reduction with LiAlFF produces the enantiomerically pure triorgano-H-silanes (A)- and (R)-RPhMeSiH (12, R = /-Pr 13, -Bu 14, /-Bu), respectively (Scheme 2). Tamao et al. have used chiral amines to prepare optically active organosilanes.157... 

A diol that has proved to be an ideal bridge is the rigid chiral [l,l -binaphthalene]-2,2 -diol which is commercially available in high optical purity in both enantiomers. Furthermore, this diol can be synthesized easily in enantiomerically pure form by phenolic oxidation25, followed by a resolution of the racemic mixture25 21. In addition, a part of this valuable chiral auxiliary can be recycled after the coupling reaction. 

Resolution of bromohydrifts.2 Diastereoisomeric esters of bromohydrins with MTPA are readily separated by fractional crystallization and characterized by NMR. The optically pure bromo MTPA esters are convertible by known methods into chiral alcohols, diols, and epoxides, including arene oxides. 

Preparative Methods racemic l,l -bi-2,2 -naphthol (BINOL) is most conveniently prepared by the oxidative coupling reaction of 2-naphthol in the presence of transition metal complexes (eq 1). The resolution of racemic BINOL with cinchonine may be performed via the cyclic phosphate (eq 2). An alternative procedure to provide directly optically active BINOL is the oxidative coupling of 2-naphthol catalyzed by Cu salt in the presence of chiral amines (eq 3). The best procedure uses (+)-amphetamine as the chiral ligand and provides BINOL in 98% yield and 96% ee. Above 25 °C the Cu /(+)-amphetamine/(5)-BINOL complex precipitates, while the more soluble Cu /(+)-amphetamine/(I )-BINOL complex is slowly transformed into the former complex. 9,9 -Biphenanthrene-10,10 -diol has also been prepared in 86% yield and with 98% ee by a similar asymmetric oxidative coupling of 9-phenanthrol in the presence of (I )- 1,2-diphenylethylamine. ... 

In the presence of a catalytic amount of the chiral titanium reagent (8) prepared from titanium tetraisopropoxide and the (/ )-1,4-diol, kinetic resolution of 5 -(2-pyridyl) thioesters of a-aryl carboxylic acids is achieved with high relative rate of both the enantiomers to give the (f )-isopropyl esters with high optical purity (eq 17). ... 

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