The chemistry of 2-aminobenzoyl hydrazides. 1. Effects of orthoester substituents on the mode of cyclization

Treatment of substituted 2-aminobenzoyl hydrazides with orthoesters has been found to yield different products depending upon the type of orthoester employed. Equimolar quantities of orthoester and hydrazide yield 3-amino-4(3H)-quinazolinones, whereas utilization of a two-fold excess (or greater) of orthoester yields, in some cases, 3,4-dihydro-5H-1,3,4-benzotriazepin-5-ones as minor products in addition to N-4(3H)-quinaz-olinon-3-yl]imidate esters as major products. Treatment of hydrazides with trimethyl orthobenzoate yields substituted 5-(2-aminophenyl)-1,3,4-oxadiazoles and 3,4-dihydro-5H-1,3,4-benzotriazepin-5-ones. The steric bulk of the phenyl group in trimethyl orthobenzoate effects the formation of adduct at the β-nitrogen of the hydrazide which cyclized to the oxadiazole and benzotriazepinone products. In the aliphatic orthoester series, the formation of adduct to the aromatic amino group appears to be favored which gives rise to quinazolinone and benzotriazepinone products.