Manganese(III) acetate mediated oxidative free-radical reactions of 2-(alkenylamino)-1,4-naphthoquinones with 1,3-dicarbonyl compounds

The manganese(III)-mediated oxidative free-radical reactions of 2-(alkenylamino)-1,4-naphthoquinones are described. The free-radical reaction of 2-(allylamino)-1,4-naphthoquinone with 1,3-dicarbonyl compounds provides a novel method for the synthesis of benzo[f]indole-4,9-diones and benzo[g]quinoline-5,10-diones. The reaction shows high chemoselectivity, depending on the solvents and 1,3-dicarbonyl compounds used. With both 1,3-diones and β-keto esters, in acetic acid, the condensation products, benzo[f]indoles, were generated selectively; in acetonitrile, the [5+1]-cyclization products, benzo[g]quinolines and tetrahydrobenzo[g]quinolines, were produced in high chemoselectivity. With diethyl malonate, the [5+1]-cyclization product, the corresponding tetrahydrobenzo[g]quinoline, was produced exclusively. The free-radical reaction of a 2-(vinylamino)-1,4-naphthoquinone with 1,3-dicarbonyl compounds produced benzo[g]quinolines effectively.