EFFICIENT GENERAL-SYNTHESIS OF 1,2-DIOL AND 1,3-DIOL IN HIGH ENANTIOMERIC EXCESS VIA THE INTRAMOLECULAR ASYMMETRIC REDUCTION OF THE CORRESPONDING KETOALKYL DIISOPINOCAMPHEYLBORINATE INTERMEDIATES

The first successful asymmetric reduction of unhindered aliphatic keto nes with B-chlorodiisopinocampheylborane is reported. In contrast to t he reduction in high ee of aralkyl ketones, such as acetophenone, with the reagent, the reduction of unhindered dialkyl ketones, such as 3-m ethyl-2-butanone, provides only poor ee. However, treatment of alpha- and beta-hydroxyketones with one equiv of diisopinocampheylborane or B -chlorodiisopinocampheylborane rapidly produces the corresponding keto alkyl diisopinocampheylborinate intermediates, which then undergo faci le intramolecular reduction. This reaction sequence, followed by oxida tive workup, provides a general synthesis of 1,2- and 1,3-diols in 84 greater than or equal to 99% enantiomeric excess. (C) 1997, Elsevier S cience Ltd.