Metalloporphyrin-catalyzed oxidation of 2-cycloalkyl-3-hydroxynaphthoquinones

Mild H2O2 oxidation of a small series of 2-cycloalkyl-3-hydroxynaphthoquino nes catalyzed by 5,-10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphineir on(III) chloride in methanol-dichloromethane leads in each case to the isol ation of a dehydro-dimer identified as a 3-cycloalkyl-3-(2-cycloalkylnaphth oquinon-3-yl)oxy-2-oxo-2,3-dihydronaphtho-1,4-quinone and in some cases to a 2-cycloalkyl-2,3-dihydroxy-1-oxoindan-3-carboxylate. The mechanism of for mation of the former is rationalized in terms of nucleophilic attack of unr eacted hydroxynaphthoquinone anion upon an epoxide primary oxidation produc t, while that of the latter is proposed to involve nucleophilic attack of s olvent methanal on the same epoxide followed by rearrangement.