Synthesis of 2-cyclopropyl-4-pyrones and 5-cyclopropyl-2-alkylene-3(2H)-furanones based on tandem cyclization-cyclopropanation strategy

In AgSbF6/Rh2(OAc)4/DCE system, two-component diastereoselective reactions of 2-diazo-3,5-dioxo-6-ynoates (phosphonates and sulphones) and alkenes provided easy access to 2-cyclopropyl-γ-pyrones through 6-endo-dig cyclization-cyclopropanation. In AgOAc/Rh2(OAc)4/Et3N/DCE system, two-component reaction of 2-diazo-3,5-dioxo-7-aryl-6-ynoates and alkenes afforded 2-cyclopropyl-2-alkylene-3(2H)-furanones through 5-exo-dig cyclization-cyclopropanation. The possible mechanism of reaction is discussed. A simple procedure and mild conditions are significant features of this strategy.