Synthesis of possible o-thioquinone methide precursors

Investigating the synthetic accessibility of o-thioquinone methide precursors containing electron donating groups, we prepared four methyl- and methoxy-substituted 2H-benzo[b]thiete derivatives by means of flash vacuum pyrolysis of the corresponding benzooxathiinone species. Methyl- and methoxy-substituted substrates proved to be compatible with the pyrolysis protocol. The pyrolysis can be performed at considerably lower temperatures and with higher yields than in previously reported syntheses of nonsubstituted 2H-benzo[b]thiete. Under proper conditions the reaction products can be isolated in excellent yields and with 100% purity, so the troublesome purification of temperature sensitive and volatile 2H-benzo[b]thiete derivatives becomes unnecessary. The sulfur-containing compounds so obtained are efficient o-thioquinone methide precursors and possible synthones for heterocyclic chemistry.Key words: 2H-benzo[b]thietes, flash vacuum pyrolysis, methyl-substituted, methoxy-substituted, o-thioquinone methide precursors.