A new reaction of dichloroketene (2) with allylic ethers, sulfides, and selenide 1 has been observed. A [3, 3] sigmatropic rearrangement takes place at room temperature, leading to cu, a'-dichloro-y J-unsaturated esters 3. The scope of this reaction was further investigated with dibromoketene (16), difluoroketene (17), electron-deficient chloroketenes, and different allylic systems. In the course of these studies, total syntheses of two naturally occurring ...
