Light-induced dehydrogenation of 2-oxo-1,2,3,4-tetrahydropyrimidine-5- carboxamides

Abstract

The light sensitivity of various 2-oxo-1,2,3,4- tetrahydropyrimidine-5- carboxamides (THPMs) was investigated by exposing them to UV light in order to elucidate the effects of the nature of the substituents located on the 4- and 5-positions of the heterocyclic ring and also the effect of an oxygen or argon atmosphere on the rate of reaction. The rate of reaction is faster under argon than under oxygen and is influenced by the nature of the substituent on the 4- and 5-positions of the THPM ring. Furthermore, it is found that the dehydrogenation of THPM-amides is faster than that of the corresponding 5-ethoxycarbonyl- and 5-acetyl-THPMs. In contrast to the solution photochemistry, no changes have been observed by irradiation in the solid state. A mechanism concerning an electron transfer from excited THPM to acetonitrile has been proposed for this reaction. © Iranian Chemical Society 2012.