Formation of 1,2,4-triazoles from the reactions of N-arylmandelamidrazones with aldehydes and with trialkyl ortho esters

Abstract

A series of N-arylmandelamidrazones has been prepared from the corresponding imidate hydrochlorides and mono- and unsymmetrically di-substituted hydrazines. The amidrazones were converted directly into 1,3,5-trisubstituted 1,2,4-triazoles by reaction with aldehydes, the more commonly reported triazolines and Schiff's bases not being observed. The triazole structure was confirmed by comparison with the products from reactions of the amidrazones with aliphatic trialkyl ortho esters. However, when, in place of the corresponding base, an amidrazone hydrochloride was treated with an ortho ester, alkylation of the benzylic hydroxy-group took place in some instances. A mechanism for this alkylation is proposed based on an intermediate isolated in a related reaction involving mandelamide.