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

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posted on 08.06.2011, 00:00 authored by Naoya Shindoh, Kazuo Kitaura, Yoshiji Takemoto, Kiyosei Takasu
The torquoselectivity of the 4π electrocyclic ring-opening reaction of 2-azetines can be controlled by the Brønsted acidity of the catalyst and the polarity of the solvent. DFT calculations provided insight into the mechanism of this remarkable switch. Anti and syn stereoisomers of α,β-unsaturated amidines were selectively synthesized from ynamides and aldimines in the presence of Tf2NH and CSA, respectively.