Thermal Decomposition of 2H-[1, 2, 4] Oxadiazolo [2, 3-a] pyridine-2-thione and 2H-[1, 2, 4] Oxadiazolo [2, 3-b] pyridazine-2-thiones : Generation of Aza-heteroaromatic α-Isocyanates and Their Utilization for the Synthesis of Unsymmetrical Disubstituted Ureas

Abstract

Thermal decomposition of 2H-[1, 2, 4] oxadiazolo [2, 3-a] pyridine-2-thione afforded 3-(2-pyridyl)-2H-pyrido [1, 2-a]-1, 3, 5-triazine-2, 4 (3H)-dione and 1, 3-di (2-pyridyl) urea, and similar decomposition of its pyridazine analog afforded 3-(3-pyridazinyl)-2H-pyridazino [1, 6-a]-1, 3, 5-triazine-2, 4 (3H)-dione and 1, 3-di (3-pyridazinyl) urea. Aza-heteroaromatic α-isocyanates, which are intermediates in the decomposition, were utilized for the synthesis of unsymmetrical 1, 3-disubstituted ureas.