Microwave- and Photoirradiation-Induced Staudinger Reactions of Cyclic Imines and Ketenes Generated from α-Diazoketones. A Further Investigation into the Stereochemical Process

Reactions of ketenes generated from α-diazoketones with a
series of acyclic and cyclic imines were investigated under
both microwave and photoirradiation conditions. The results
indicate that the zwitterionic azabutadiene-type intermediates yielded from imines and ketenes undergo a conrotatory
ring closure exclusively to produce β-lactams. It is notable
that no Woodward−Hoffmann product was found under the
ultraviolet irradiation. The photoirradiation-induced Staudinger reaction shows a different stereoselectivity from the
electrocyclic reaction of substituted 1,3-butadiene.