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

Abstract

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