Catalyst-Controlled Torquoselectivity Switch in the 4π Ring-Opening Reaction of 2-Amino-2-azetines Giving β-Substituted α, β-Unsaturated Amidines

摘要

The torquoselectivity of the 4π electrocydic ring-opening reaction of 2-azetines can be controlled by the Brensted acidity of the catalyst and the polarity of the solvent. DFT calculations provided insight into the mechanism of this remarkable switch. And and syn stereoisomers of α,β-unsaturated amidines were selectively synthesized from ynamides and aldimines in the presence of Tf_2NH and CSA, respectively.