Manganese (III) Acetate Mediated Free Radical Cyclization of 1,3-Dicarbonyl Compounds with Sterically Hindered Olefins

摘要

The manganese(III) acetate mediated radical cyclization of dimedone la,2,4-pentanedione 1b,ethyl acetoacetate 1c,1,3-cyclohexanedione 1d and 5-phenyl-l,3-cyclohexanedione 1e with 1,1-diphenyl-1-butene 2a afforded 4,5-dihydrofurans (3c,3e) and tetrahydrobenzofurans (3a,3g,3h) in good yields (55% - 77%).Additionally,the reactions of trifluoromethyl-group containing 1,3-dicarbonyls,4,4,4-trifluoro-1-phenylbutane-1,3-dione 1f and 4,4,4-trifluoro-l-thien-2ylbutane-1,3-dione 1g with 2a 3-trifluoroacetyl-4,5-dihydrofurans gave in 74% and 78% yields,respectively.Treatment of 1a,1b and 1c with 1,2-diphenyl-1-pentene 2a resulted in the formation of tetrahydrobenzofuran 3b and 4,5-dihydrofurans 3d and 3f in lower yields.