RADICAL-MEDIATED CYCLIZATION OF OMEGA-ARYL-BETA-DICARBONYL COMPOUNDS TO TETRAHYDROBENZOCYCLOHEPTEN-6-ONES, HEXAHYDROBENZOCYCLOOCTEN-6-ONES AND NAPHTHALEN-2(1H)-ONES

Manganese(III) acetate in acetic acid promotes efficient radical-media ted oxidative cyclisation of epsilon-aryl-beta-dicarbonyl and Z-gamma, delta-unsaturated delta-aryl-beta-dicarbonyl compounds carrying electr on-releasing groups in the aromatic ring, forming 6,7,8,9-tetrahydro-5 H-benzocyclohepten-6-ones and naphthalen-2(1H)-ones, respectively, The process is accompanied by secondary acetoxylation at the activated be nzylic position bf the initial cyclisation products, and. is exemplifi ed by the conversions of the epsilon- and delta-aryl-beta-dicarbonyl c ompounds 6 and 11 into the benzocycloheptenone 18 and the naphthalenon e 21, respectively, Application of the oxidation to the formation of 8 -membered hexahydro- and tetrahydro-benzocycloocten-6-ones 19 and 22 f rom zeta-aryl-beta-dicarbonyl and Z-gamma,delta-unsaturated zeta-aryl- beta-dicarbonyl compounds is limited by low reactivity, and in the lat ter case, by radical rearrangement followed by cyclisation to a tetral in.