Studies on sulphur heterocycles. Reactions of 6,7-dihydrobenzo[b]thiophen-4(5H)one derivatives and their conversion to 7-substituted thieno[2,3-h][1]benzopyran-8-ones

Cyclization of γ-(2-thienyl)butryic acid with acid anhydrides gives 2-acyl derivatives as well as the expected 6,7-dihydrobenzob]thiophen-4(5H)one. Several reactions of these ketones have been studied including their conversion to 0,0-diethyl thiophosphonohydrazones. 7-Substituted thieno2,3-h]1]benzopyran-8-ones have been prepared via 4-hydroxybenzob]thiophen-5-carbaldehydes.