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.
1-Aryl-1-nitroso-3-(2-pyridylmethyl)ureas在
丙酮、
氯仿或
乙醚中加热后环化为2-aryl-5-(2-pyridyl)-2, 4-dihydro-1, 2, 4-triazol-3-ones,产率在59-86%之间。它们的结构通过X射线晶体学得到证实,2, 4-dihydro-1, 2, 4-triazol-3-one环的分子几何结构与相关的两性离子环状化合物的分子几何结构进行了比较。对相应的4-
吡啶衍生物1-aryl-1-nitroso-3-(4-pyridylmethyl)urea进行类似处理后,没有得到任何环化化合物,而1, 3-bis(4-pyridylmethyl)urea的产率达到了60%。上述反应的机理已经提出。