A new system for catalytic enantioselective reduction of achiral ketones to chiral alcohols. Synthesis of chiral α-hydroxy acids

Abstract

The reduction of a variety of achiral ketones with catecholborane as stoichiometric reductant and 0.1 equiv of oxazaborolidine 2 as catalyst in toluene at −78°C proceeds in > 95% yield and with enantioselectivities in the range 30:1 to 9: 1, depending on substrate. This reduction procedure is especially advantageous for α,β-enones, thereby providing chiral precursors for a great variety of compounds, for example, α-hydroxy acids.