α-Amino Acids Mediated C−C Double Bonds Cleavage in Diastereoselective Synthesis of Aza-Spirocyclic Pyrazolones

Abstract

An efficient and reagent-free synthesis of highly functionalized aza-spirocyclic pyrazolones are achieved from easily available α-amino acids and alkylidene pyrazolones by means of amination, C−C-double bonds cleavage, and decarboxylative annulation process. These highly diastereoselective reactions are promoted simply by α-amino acids and involve in situ generated azomethine ylides as reactive intermediates. This newly developed protocol involves the formation of three new bonds (one C−N and two C−C) and four new contiguous stereo-centers including a quaternary carbon center in a single pot cascade process. (Figure presented.). © 2020 Wiley-VCH GmbH