Intramolecular S(N)2 reaction alpha- to a trifluoromethyl group: preparation of 1-cyano-2-trifluoromethylcyclopropane

The first intramolecular S(N)2 reaction of alpha-trifluoromethylated second ary alcohols by a carbanion is described. A stereoselective intramolecular cyclization of 3-substituted-3-cyano-1-trifluoromethylpropyl sulfonate via the cyano stabilized carbanion provides 1-substituted-1-cyano-2-trifluorome thylcyclopropanes in good yields. The product has the opposite configuratio n to the starting alcohol at the carbon attached to trifluoromethyl group, revealing the reaction takes place in S(N)2 manner with Walden inversion at the reaction center. (C) 1999 Elsevier Science Ltd. All rights reserved.