Aminoborohydrides. 5. Reduction of Alkylcyclohexanones to the Corresponding Alcohols with Unique Steric Selectivity

Article abstract of DOI:10.1016/S0040-4039(00)77063-8

Lithium aminoborohydrides (LAB), obtained by the reaction of n-butyllithium with aminoboranes, are powerful reducing agents for a wide range of functional groups including the carbonyl group of alkylcyclohexanones.Reduction of 2-methylcyclohexanone with LAB reagents shows superior formation of the axial alcohol as compared to sodium borohydride (NaBH4).Reduction of 3- and 4-methylcyclohexanones shows formation of the equatorial alcohol in proportions similar to that obtained with NaBH4.Reduction of 4-tert-butylcyclohexanone leads predominantly to the corresponding cyclohexanol containing an equatorial alcohol group.Unlike NaBH4, LAB reagents are soluble in ether solvents allowing for homogeneous reductions.