Synthesis of Thienyl-Substituted Dihydrofuran Compounds Promoted by Manganese(III) Acetate

Radical cyclization reactions of both aliphatic 1,3-diones 1a and 1b and of cyclic 1,3-diones 1c1e with 2-thienyl- and 3-thienyl-substituted alkenes 2a2d in the presence of manganese(III) acetate were investigated. Thienyl-substituted dihydrofurans 3 were obtained with moderate to high yields (Table 13). Also, the favorable effect of the thienyl substituent on the intermediate carbocation stability was evaluated by comparison with a phenyl substituent.