A New Powerful Approach to Multi-Substituted 3(2H)-Furanones via Brønsted Acid-Catalyzed Reactions of 4-Diazodihydrofuran-3-ones

The interaction of 5,5-dialkyl(diaryl)-substituted 4-diazo-3(2 H )furanones with Brønsted acids (TFA, TsOH, etc.) causes elimination of nitrogen accompanied by 1,2-nucleophilic rearrangement, giving rise to exclusive formation of 4,5-dialkyl(diaryl)-substituted 3(2 Н )-furanones, ring-fused 3(2 H )-furanones, and phenanthro[9,10- b ]furan-3(2 H )-ones in yields of up to 99%. The reaction is a new highly efficient way for the synthesis of multisubstituted 3(2 Н )furanones.