Stereoselective 1,5-rearrangement of vinylketene-N,O-acetals: novel vinylogous Ferrier reaction

Vinylketene-N,O-acetals underwent Lewis acid-induced 1,3- or 1,5-rearrangement to afford the corresponding C-alkylated products. 1,5-Rearrangement proceeded predominantly in dichloromethane, and it is quite interesting to achieve an unprecedented high degree of asymmetric induction in such a remote position. Crossover experiments indicated that the reaction proceeded through an ion pair intermediate.