Intramolecular SN2 reaction α- to a trifluoromethyl group:: preparation of 1-cyano-2-trifluoromethylcyclopropane

The first intramolecular S(N)2 reaction of alpha-trifluoromethylated secondary 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-trifluoromethylcyclopropanes in good yields. The product has the opposite configuration 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.