Imino ene reactions in organic synthesis

During the last decade the ene reaction has achieved wide recognition as a powerful carbon-carbon bond forming method in synthetic organic chemistry. The imino ene reaction, however, is still a relatively rare transformation despite its potential for preparation of nitrogen heterocycles and in alkaloid total synthesis. This review describes mechanistic aspects of the imino ene reaction and illustrates a number of synthetic applications of this versatile process. The details of inter- and intramolecular imino ene reactions involving N-alkyl, N-acyl, and N-sulfonyl imines or iminium ions are presented with particular emphasis on the regio- and stereochemical issues accompanying these processes. A discussion of retro imino ene reactions is also included.