The Dimroth rearrangement. Part VI. The abnormal behaviour of 5-cyano-1,2-dihydro-2-imino-1-methylpyrimidine

Abstract

5-Cyano-1,2-dihydro-2-imino-1-methylpyrimidine rapidly undergoes normal or abnormal Dimroth rearrangements according to the conditions. At room temperature, a mildly alkaline solution yields the acyclic intermediate, N-(2-cyano-2-formylvinyl)-N′-methylguanidine, which can be variously cyclised. By warming the intermediate or the original pyrimidine in dilute aqueous ammonia, the normal product, 5-cyano-2-methylaminopyrimidine, is formed; in aqueous sodium hydroxide, an abnormal product, 4-amino-5-formyl-1,2-dihydro-2-imino-1-methyl-pyrimidine, results from the addition of the methylamino-group to the cyano-group at the intermediate stage. This iminopyrimidine slowly undergoes a second abnormal Dimroth rearrangement to 5-carbamoyl-2-methyl-aminopyrimidine.