Allenoates in Enantioselective [2+2] Cycloadditions: From a Mechanistic Curiosity to a Stereospecific Transformation.

ABSTRACT: Identification of a novel catalyst-allenoate pair allows enantioselective [2+2] cycloaddition of α-methylstyrene. To understand the origin of selectivity, a detailed mechanistic investigation was conducted. Herein, two competing reaction pathways are proposed, which operate simultaneously and funnel the alkenes to the same axially chiral cyclobutanes. In agreement with the Woodward-Hoffmann rules, this mechanistic curiosity can be rationalized through a unique symmetry operation that was elucidated by deuteration experiments. In the case of 1,1-diarylalkenes, distal communication between the catalyst and alkene is achieved through subtle alteration of electronic properties and conformation. In this context, a Hammett study lends further credibility to a concerted mechanism. Thus, extended

SUBMITTER: Wahl JM 

PROVIDER: S-EPMC6295144 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature