Vinylindenes and Some Heteroanalogues in the Diels-Alder Reaction, VII. Vinylbenzo[b]thiophens and 1,4-Naphthoquinone

Abstract

A mechanism postulated for the base-catalysed oxidative rearrangement of 5,5a,6,12a,12b,13-hexa-hydroanthra[l,2-b]benzo[d]thiophen-5,13-dione (the adduct of 3-vinylbenzo[b]thiophen and 1,4-naph-thoquinone) to anthra[2,3-b]benzo[d]thiophen-7,12-quinone is supported by isolation of a 5a,6-di-hydro derivative when the reaction is carried out in the absence of oxygen. Similar derivatives are formed from two methyl homologues of the adduct. Conditions are described for conversion of the adducts into 6,7-dihydroanthra[l,2-b]benzo[d]thiophen-5,13-quinones, and it is also shown that 2-methyl-3-vinylbenzo[b]thiophen and 1,4-naphthoquinone give an adduct in which the diene has undergone isomerization before adduct formation.