[1,4] and [2,3] Sigmatropic rearrangements of ylides generated from N-(α-cyano)allyl-N-cyanomethyl-N,N-dimethylammonium perchlorates

Abstract

N-(α-Cyano)allyl-N-cyanomethyl-N,N-dimethylammonium perchlorates 3a–c when treated with solid K₂CO₃–DMSO (system A) afforded the α-cyano enamines 6a–c by a [1,4] shift of the α-cyano allylides 4a–c^+–; when treated with solid NaHCO₃–DMF (system C), however, these gave α-amino nitriles 8a–c, by a [2,3] shift of the cyano methylides 5a–c^+–. Reaction of the salts 3a,b with aq. NH₃–CH₂Cl₂(system B) led to the formation to 8a,b, while the salt 3c, under the same conditions, yielded a mixture of 6c and 7c. It is postulated that the high tendency of 3a–c to undergo a [1,4] shift via the respective ylides, in contrast to the corresponding benzylammonium salts, is due to a different charge distribution in the anionic parts of the allylides and benzylides.