Stereo- and regiocontrol of electrophile-initiated rearrangement of push-pull 5-substituted 4-oxothiazolidine derivatives

Regioselective a-bromination of (Z)-5-substituted-2-alkylidene-4-oxothiazol idine derivatives affords, under mild experimental conditions, vinyl bromid es 3 in good yields. They undergo rearrangement providing a highly efficien t route to the stereodefined 4-oxo-thiazolidine derivatives possessing two fully delocalized exocyclic double bonds at C(2) and C(5) positions. A mech anism of this novel rearrangement reaction via base-promoted proton transfe r from one carbanionic site to another, followed by the bromination-dehydro bromination sequence, is proposed. (C) 2001 Elsevier Science Ltd. All right s reserved.