Reactions of secondary beta-ketothioamides with ethyl bromoacetate and ethyl 2-bromopropionate. The synthesis of N-substituted 2-acylmethylidene-1,3-thiazolidin-4-ones

4-Morpholinocoumarin (2) was obtained in the reaction of 4-(2-hydroxythiobe nzoyl)morpholine (1) with ethyl bromoacetate in the presence of triphenylph osphine and triethylamine. Analogous reactions of 3-keto thioamides with et hyl bromoacetate and ethyl 2-bromopropionate, carried out in THF or acetone , yielded cyclic derivatives of N-substituted 2-acylmethylidene-1,3-thiazol idin-4-ones (4, 7, 8). In the reaction with ethyl 3-bromopropionate only S- alkylation of the thioamide was observed. The reaction of the indandione-de rived thioamides 6 with ethylbromoacetate in acetone gave the condensation products of 2-acylmethylidene-1,3-thiazolidin-4-ones with acetone. 2-Acylme thylidene-1,3-thiazolidin-4-ones 4, 7, 8 condensed with benzaldehyde to giv e the 5-benzylidene derivatives.