Isothiourea-catalysed chemo- and enantioselective [2,3]-sigmatropic rearrangements of N,N-diallyl allylic ammonium ylides

Abstract

The isothiourea-catalysed chemo- and enantioselective [2,3]-sigmatropic rearrangement of N,N-diallyl allylic ammonium ylides is explored as a key part of a route to free functionalised α-amino esters and piperidines. The [2,3]-sigmatropic rearrangement proceeds with excellent diastereo- and enantiocontrol (>95:5 dr, up to 97% ee), with the resultant N,N-diallyl α-amino esters undergoing either mono- or bis-N-allyl deprotection. Bis-N-allyl deprotection leads to free α-amino esters, while the mono-deprotection strategy has been utilized in the synthesis of a target functionalised piperidine.