On triazoles. XL [1]. Non catalytic dehalogenation of some 5‐chloro‐1,2,4‐triazolo[1,5‐a]pyrimidine derivatives

Abstract A non catalytic dehalogenation method of type 4 5‐chloro‐ 1 ,2,4‐triazolo[1,5‐ a ]pyrimidine derivatives based on the hydrolysis of the corresponding type 5 p ‐toluenesulphonyl hydrazones with diluted aqueous sodium carbonate solution was elaborated. The method provides the required 5‐unsubstituted derivatives 6 also in those cases when the simple hydrogenation is not possible. Using deuterium oxide as the solvent of the hydrolysis, deuterium atoms also could be inserted into position 5 of derivatives 6 . Different by‐products of the reactions were also isolated, and a possible explanation was given for their formation.