Regioselective Synthesis of 4′-amino-1′H-spiro[cyclohexane-1,2′-(pyrimido [1,2-a]benzimidazole)]-3′-carbonitrile in Aqueous Medium

A simple, mild and environment-friendly procedure for synthesis of 4′-amino-1′H-spiro[cyclohexane-1,2′-(pyrimido[1,2-a]benzimidazole)]-3′-carbonitrile is developed using microwave irradiation in water. The product is obtained in short time, in excellent yield, and in a good state of purity. The reaction pathway and the influence of reaction conditions on regiochemistry are also investigated. The regioselectivity in this process is confirmed chemically and by single-crystal X-ray molecular structure determination.