[2 + 2] Cycloaddition Reactions of Imines with Alkynyl Selenides Catalyzed by Scandium Triflate.

It was found that a new reaction of imines with alkynyl selenides proceeded smoothly in the presence of a catalytic amount of Sc(OTf)3 affording α,β-unsaturated selenylimidates. These reactions are assumed to proceed by a [2+2] cycloaddition of the imines to the alkynyl selenides to form azetine intermediates, which are unstable and immediately fragment to the corresponding α,β-unsaturated selenylimidates.