Kinetics of reduction of acetophenones by alkali-metal alkoxides, and the mechanism of reduction of ketones by borohydride

Abstract

The reduction of p-substituted acetophenones by lithium, sodium, and potassium isopropoxides gives Hammett reaction constants (ρ) of +1.45, +1.62, and +1.75. respectively. Comparison with data for reductions of acetophenones by borohydride supports the view that the transition state for reduction of ketones by borohydride is product-like. Stereochemical variations in the reduction of steroidal ketones by borohydrides are reinterpreted in terms of ‘steric strain control’ as the principal contributing factor.