A simple method for the synthesis of 5-(het)aryl-3-cyano-1-ethyl-2(1H)-pyrazinones was proposed. The method is based on the hydrolysis of the corresponding 2,3-dicyanopyrazinium salts. The spectral properties of pyrazinones were studied and their crystallographic investigation was carried out. The possibility of introduction of 5-(het)aryl-3-cyano-1-ethyl-2(1H)-pyrazinones into the [2+4] cycloaddition under the microwave activation conditions was sho