Enantioselective [1,2]-Stevens rearrangement of quaternary ammonium salts. A mechanistic evaluation

摘要

Using a supramolecular asymmetric ion pairing strategy, an enantioselective |l,2]-Stevens is feasible on substrates devoid of stereogenic quaternary nitrogen atoms. The [1,2]-Stevens rearrangement, which is the spontaneous transformation of ammonium ylides into tertiary amines, has been strongly studied for its interesting mechanism and for its synthetic utility.1 Despite the many studies, asymmetric versions of this reaction still remain a challenge probably reflecting the radical character of the process.