Enantioselective Ketone Reduction Chiral Reagent

Asymmetric reduction of acetylenic ketones using Alpine borane

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R-Alpine borane is effective at reducing acetylenic ketones to secondary alcohols with reasonable enantioselectivity. The enantioselection arises through the selective placement of the sterically undemanding alkyne close to the methyl substituent in the boat transition state for the reduction.

M. M. Midland, Chem. Rev., 1989, 89, 1553–1561.