Asymmetric 'Clip-Cycle' synthesis of 3-spiropiperidines.

Abstract

3-Spiropiperidines can be synthesized in up to 87% yield and 96 : 4 er using a two step 'Clip-Cycle' approach. The 'Clip' stage of this method is based on efficient and highly E-selective cross metathesis of N-Cbz-protected 1-amino-hex-5-enes with a thioacrylate. This is followed by the 'Cycle' step, in which an intramolecular asymmetric aza-Michael cyclization is promoted by a chiral phosphoric acid catalyst.