HELVETICA CHIMICA ACTA, vol.95, no.5, pp.795-804, 2012 (SCI-Expanded)
The 2-thienyl-substituted 4,5-dihydrofuran derivatives 38 were obtained by the radical cyclization reaction of 1,3-dicarbonyl compounds 1a1f with 2-thienyl-substituted conjugated alkenes 2a2e by using [Mn(OAc)3] (Tables 15). In this study, reactions of 1,3-dicarbonyl compounds 1a1e with alkenes 2a2c gave 4,5-dihydrofuran derivatives 35 in high yields (Tables 13). Also the cyclic alkenes 2d and 2e gave the dihydrobenzofuran compounds, i.e., 6 and 7 in good yields (Table 4). Interestingly, the reaction of benzoylacetone (=1-phenylbutane-1,3-dione; 1f) with some alkenes gave two products due to generation of two stable carbocation intermediates (Table 5).