Cyclization of 1-Aryl-1-nitroso-3-(2-pyridymethyl)ureas to 2-Aryl-5-(2-pyridyl)-2, 4-dihydro-1, 2, 4-triazol-3-ones

Abstract

1-Aryl-1-nitroso-3-(2-pyridylmethyl)ureas cyclize to 2-aryl-5-(2-pyridyl)-2, 4-dihydro-1, 2, 4-triazol-3-ones on being heated in acetone, chloroform or ether, in 59-86% yields. Their structures were condirmed by X-ray crystallography, and the molecular geometry of the 2, 4-dihydro-1, 2, 4-triazol-3-one ring is discussed in comparison with those of related zwitterionic ring compounds. Similar treatment of the corresponding 4-pyridyl derivative, 1-aryl-1-nitroso-3-(4-pyridylmethyl)urea did not give any cyclized compound, and 1, 3-bis(4-pyridylmethyl)urea was obtained in 60% yield. Mechanisms are proposed for the above reactions.