Manganese(III)-mediated oxidative annulation of methylenecyclopropanes with 1,3-dicarbonyl compounds

Manganese(III)-mediated oxidative annulation of methylenecyclopropanes with 1,3-dicarbonyl compounds in acetic acid produces 4,5-dihydrofuran derivatives as [3+2] annulation products in moderate to good yields under mild conditions. The possible reaction mechanism is discussed on the basis of previous mechanistic investigation.