Lithium dimesitylborohydride reduction

Carbonyl Reactivity—The reagent lithium dimesitylborohydride bis(dimethoxy-ethane), which has been isolated and whose crystal structure has been reported, may be employed as a stereoselective reducing agent Thus after 3 h at 0°C in di-methoxyethane 2-, 3-, and 4-methylcyclohexanones were reduced respectively to the cis- (99 %), trans- (99 %), and cis- (94 %) alcohols. However, 3 days, at 25°C, were required for complete reduction of camphor to give 99.8 % isoborneol. 

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