Ketenimines from Isocyanides and Allyl Carbonates: Palladium-Catalyzed Synthesis of β,γ-Unsaturated Amides and Tetrazoles

The reaction of allyl ethyl carbonates with isocyanides in the presence of a catalytic amount of Pd(OAc)(2) provided ketenimines through -hydride elimination of the allyl imidoylpalladium intermediates. The insertion of the isocyanide into the -allyl Pd complex proceeded via an unusual (1)-allyl Pd species. The resulting ketenimines were hydrolyzed to ,-unsaturated carboxamides during purification by flash column chromatography on silica gel or converted insitu into 1,5-disubstituted tetrazoles by [3+2] cycloaddition with hydrazoic acid or trimethylsilyl azide.