Preparation of Enantiomerically Enriched Bromohydrins from [N-(p-Tolylsulfonyl)sulfoximino]oxiranes Using in situ Reduction of α-Bromo Aldehydes.

Treatment of enantiomerically pure [N-(p-tolylsulfonyl)sulfoximino]oxiranes 6 with MgBr2 in the presence of tetrabutylammonium borohydride gives enantiomerically enriched bromohydrins 3, together with small amounts of the primary alcohols 11. The bromohydrins 3 are isolated in good yields with enantiomeric excesses in the range 70% to 91%. This process establishes that α-bromo aldehydes have sufficient configurational stability to be viable synthetic intermediates.