Cyclohexanone derivatives stereoselective reduction

A sterically demanding PhMe2Si group at the C-3 position of 1-cyclohexanone derivatives affects a highly stereoselective reduction of the C-l carbonyl group by NaBI-L in methanol187. The 3-silyl-l-cyclohexanol product holds a cis configuration. 

Reduction. The dichloride is a reducing agent similar to mixed hydride (HAlCy and it is fairly stereoselective in the reduction of cyclohexanone derivatives in that... 

Research activities on heterogeneously-catalyzed stereoselective reductions have generally increased during the past years[l]. Among various functionalities the stereoselective aromatic ring reduction is of importance in the synthesis of fine chemicals such as pharmaceuticals, herbicides, fragrances and liquid crystals. Particularly, substituted phenol derivatives offer the possibility to control the product selectivity via reduction of the prochiral intermediate cyclohexanone [2,3]. 

Secondary Amines.—The reduction of imines to the corresponding secondary amines can be effected by various methodologies. New additions are the sodium triacyloxyborohydrides (easily obtainable from sodium borohydride and AT-acyl derivatives of optically active amino-acids), which are used for the asymmetric reduction of cyclic imines. Also now available is a highly stereoselective reduction of N-benzylimines derived from substituted cyclohexanones, with alkali-metal borohydrides, in particular L-selectride. A fiuther addition is the first report of the reduction of aldimines by hydrogen transfer from propan-2-ol,... 

MAD and MAT have played a crucial role in the stereoselective synthesis of hitherto inaccessible equatorial carbinols from cyclohexanones and primary allyl Grignard reagents or methyllithium [44). In the reaction of cyclohexanone derivatives with tert-butylmagnesium chloride, reduction takes precedence over alkylation in the presence of MAD (Scheme 6.37) [45). 

In analogy to 23, the chiralities of [2.2]meta- and [10]paracyclophanecarboxylic acids were also deduced from the results of kinetic resolutions 40-77>. For the application of Horeau s method, (—)-[10]paracyclophanecarboxylic acid (14) was transformed by stereoselective hydrogenation and subsequent sodium borohydride reduction of an intermediate cyclohexanone into the (—)-cis-cyclohexanol 94 which on reaction with racemic 2-phenylbutanoic anhydride afforded a 15% excess of the Ievorotatory acid thereby proving (in agreement with the kinetic resolution of the anhydride of 14, vide supra) the chirality (5) for (—)-14 and all its derivatives 40). Optical comparison with dioxa[10]paracyclophanecarboxylic acid (16) confirmed this result63,108). 

Several olha- syntheses of cyclohexane-containing natural products reported also utilized Fenier rearrangement as a key step. A synthesis of a compactin analogue involved conv aon of the 1,6-anhydro-D-glucose-derived 44 to cyclohexanone 45, which was further elaborated to 46 en route to die natural product, via elimination, stereoselective ketone reduction, cuprate methyl Sn2 ... 

The solid complex (7), derived from sodium borohydride and mandelic acid, has been found to be a milder reducing agent than sodium borohydride, with the same stereoselectivity as lithium aluminium hydride for the reduction of substituted cyclohexanones the reagent from (- -)-(5)-mandelic acid gave only low asymmetric induction (11.5% e.e.) in the reduction of acetophenone. 

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