Ring opening and closing reactions of imidazoles and other 1,3-diazaheterocycles with vinyl chloroformate and phenyl chloroformate

Treatment of imidazole and benzimidazole with vinyl chloroformate or phenyl chloroformate in weakly alkaline aqueous solution leads to their conversion into the corresponding imidazol-2-ones; in weakly acidic solutions these chloroformates convert adenine into isoguanine, 6-methylaminopurine into 1-methylisoguanine and pyrimidine into an acyclic product.