Selenium heterocycles. XV. Reaction of 2-aminoselenazoles and 2-amino-1,3,4-selenadiazoles with acetylenic compounds

2-Aminoselenazoles with ethyl propiolate or dimethyl acetylenedicarboxylate gave 7H-selenazolo3,2-a]pyrimidin-7-ones. 2-Amino-1,3,4-selenadiazoles with dimethyl acetylenedicarboxylate gave 7H-1,3,4-selenadiazolo3,2-a]pyrimidin-7-ones; with ethyl propiolate the reaction took an unusual path and 2-carbethoxy-5H-selenazolo3,2-a]pyrimidin-5-one was isolated. The assignment of the structures were supported by spectra analysis.