5,10-Dihydro triazolo quinazolines

The reaction of 2,3-diaminoquinazolin-4-one 404 with aryl aldehydes and thioglycolic acid gives 2-substituted 1,3-dihydro-thiazolo[3, 4 2,3][l,2,4]triazolo[5,l-A]quinazolin-5-ones 405 (Equation 79) <2004MI10>. 

Another general route to 5,10-dihydro[l,2,4]triazolo[5,l-b]quinazolines via the electrocyclization of an azino carbodiimide intermediate has been described (94S1057). The key iminophosphorane, a benzophenone-1-[(triphenylphosphoranylidene)amino]ethylidenehydrazone, was easily prepared in a Kirsanov-variant first applied by Bayless and Zimmer (68TL3811). It consists of the reaction of triphenylphosphine/iodine/trieth-ylamine with benzophenone 1-aminoethylidenehydrazone (94SI057). 

The investigations (66JCS(C)2290) on the reactivity of this ring system have centered around 5-oxo-3-phenyl-4,5-dihydro-[l,2,3]triazolo[l,5-fl]quinazoline (see Scheme 17) whose preparation is given in Section 4.15.4.6.4. The latter two reactions in Scheme 17 resemble those discussed previously for [l,2,3]triazolo[l,5-a]pyrimidines and depicted in Scheme 12. 

A representative of this ring system (namely, 5-oxo-3-phenyl-4,5-dihydro[l,2,3]triazolo[l,5-n]quinazoline (335)) has been prepared by the reaction between o-azidobenzoic acid and phenylacetonitrile in the presence of sodium methoxide (66JCS(C)2290). This is illustrated in Scheme 57. 

A three-component condensation of 3-amino-l, 2,4-triazole (or its 5-Me and 5-methylthio derivatives), 1 and DMF-dimethylacetal afforded 8,9-dihydro[l,2,4]triazolo[l,5-fl]quinazolin-6(7H)-ones (06RCB1224). Condensation of 3,4,5-triamino-l,2,4-triazole with aromatic aldehydes and dimedone afforded partially hydrogenated 9-aryl-[l,2,4]triazolo[5,l-frJquinazolin-8-ones. The structure of 2-amino-6,6-dimethyl-3-(4-nitro-benzylidene)amino-9-(4-nitrophenyl)-5,6,7,9-tetrahydro[l,2,4]triazolo[5,l-fr]-quinazolin-8-one was confirmed by X-ray analysis (05RCB2903). 

Much as in previous years, the majority of 1,2,4-T preparations have involved synthesis of ring fused species. Thus, final-step cyclization to the triazole has provided mesoionic triazolo [4,3-a]quinoxalines <97JHC1539>, 1,2-dihydro-l,2,4-triazolo[3,2-b]quinazolin-... 

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