Oxidative Free Radical Cyclization of 2-(Ethoxycarbonylmethyl)-1,4-naphthoquinone Derivatives

Abstract A manganese(III)-mediated oxidative free radical cyclization of 2-(ethoxycarbonylmethyl)-1,4-naphthoquinone derivatives is described. These starting 2-(ethoxycarbonylmethyl)-1,4-naphthoquinones can be synthesized effectively from the reaction of corresponding 1,4-naphthoquinones with ethyl nitroacetate. With 2-benzyl-3-(ethoxycarbonylmethyl)-1,4-naphthoquinones, naphthacene-5,12-diones were produced effectively in high selectivity. With ethyl 2-benzoyl-3-(ethoxycarbonylmethyl)-1,4-naphthoquinones, in addition to the expected 6-hydroxynaphthacene-5,12-diones, the novel naphtho[2,3-C]furan-4,9-diones were also formed as the major product.