Radicalcyclizationreactions of both aliphatic 1,3‐diones 1a and 1b and of cyclic 1,3‐diones 1c–1e with 2‐thienyl‐ and 3‐thienyl‐substituted alkenes 2a–2d in the presence of manganese(III) acetate were investigated. Thienyl‐substituteddihydrofurans 3 were obtained with moderate to high yields (Table 1–3). Also, the favorable effect of the thienyl substituent on the intermediate carbocation stability