Synthesis of Furan-2(5H)-ones via Oxidative Free-Radical Cyclization

Significance

An efficient synthesis of furan-2(5H)-ones involving a manganese(III)-based oxidative free-radical cyclization of dimethyl malonates or ethyl cyanoacetates with allenes is reported. Only disubstituted allenes with one obligatory aryl group may be used for this process. Otherwise, dimethyl 2-(2-oxoethylidene)malonates or unidentified products are formed. A mechanism involving a cationic intermediate A, formed by a manganese(III)-induced oxidative initiation and termination of free-radical species is proposed. The final steps in the proposed mechanism are unexceptional.