Synthesis of 2-azaspiro[4.4]nonan-1-ones via phosphine-catalysed [3+2]-cycloadditions

The phosphine-catalyzed [3+2]-cycloaddition of the 2-methylene γ-lactams and and the acrylate with the ylides derived from the ethyl ester, the amide or the chiral camphor sultam derivative of 2-butynoic acid () give directly, or indirectly after reductive cyclization, spiro-heterocyclic products. The acid underwent Curtius rearrangement and then acid hydrolysis to give two novel spiro-cyclic ketones, and .