An Unusual Course of the Schmidt Rearrangement in the Reaction of 2H-Azirine-2-carbonyl Azides with Unsaturated Diazoesters

Abstract— In the reaction of 2H-azirine-2-carbonyl azides with vinyldiazoacetates at ambient temperatures in the absence of an effective oxidant, a competition takes place between the rearrangement of the azidohydrin intermediate of the Schmidt reaction, leading to pyridine-3-isocyanate, and the decomposition of the intermediate to form deaminated pyridine and cyanic acid. The driving force behind both processes is the elimination of a nitrogen molecule. In the presence of an effective oxidizing agent in the reaction medium, the main process is the Curtius rearrangement of the pyridinecarbonyl azide intermediate, leading to pyridine-3-isocyanate.