Donald J. Dumas

Preparation of 3,4-diaryl-4,5-dihydro-1H-1,2,4-triazole-1-N-phenylcarboxamides

N 3 -Arylbenzamidrazone (5) reacts with aldehydes and ketones to give the corresponding hydrazones (6) rather than the tautomeric 4,5-dihydro-1 H-1,2,4-triazoles (7). Treatment of the hydrazones (6) with α,α,α-trifluoro-p-tolyl isocyanate gives 3,4-diaryl-4,5-dihydro-1 H-1,2,4-triazole-1-carboxamides (8). This suggests that, in solution, hydrazones (6) exist in equilibrium with low levels of the more nucleophilic 4,5-dihydro-1 H-1,2,4-triazoles (7) which are trapped by isocyanate to give triazolines of formula (8)