Synthesis of Various Dihydro–Thiazole and Selenazole Heterocycles

Abstract We prepared numerous thiazole derivatives from push‐pull alkenes such as nitroenamines, enaminoester, and enaminonitrils in a two‐step reaction with thiocyanate ion. The first step was the formation of the thiocyanate‐substituted push‐pull alkene from an iodine‐containing intermediary. We demonstrated this sequence through the preparation and identification of the iodine‐substituted enamines. In the second step, thiazole ring closure took place in methanol, at room temperature. The imino group of the condensed thiazole ring systems was successfully acylated. The same reaction sequence with potassium selenocyanate resulted in two selenocyanate and a selenazole heterocyclic derivatives. The mechanism of the reaction with thiocyanate ion and the heterocycle formation was investigated by computational methods. We performed quantum chemical calculations, involving both the thermodynamic and the kinetic aspects of the ring closure reaction.