p-Tolyl 2-thienyl ketone (I) condensed with dimethyl succinate in the presence of potassium t-butoxide to give the trans (SC,H,/CO,Me) half-ester (IIIa) whose configuration was deduced by cyclization to the corresponding benzo[b]thiophene derivatives. Carbamates, esters, cyclic hydrazides and substituted phenolic and acetic acids useful as antibacterial and antiinflamatory agents were obtained. T h e reaction of ketone I with malononitrile to give ylidenemalononitrile I1 was also considered.