A highly efficient and stereospecific borane reduction of spiro[4,4]nonane-1,6-dione catalyzed by a chiral oxazaborolidine

A highly stereoselective and enantioselective reduction of racemic spiro[4,4]nonane-1,6-dione catalyzed by an oxazaborolidine reagent is described. The asymmetric reduction of the racemic spirodiketones resulted in enantiomerically pure spirodiols which are useful chiral auxiliaries and also key intermediates for the synthesis of other highly effective chiral ligands. The trans,trans- and cis,trans-spirodiols were prepared in high enantiopurity by employing chiral oxazaborolidine as the catalyst.