1.2.4- Triazolo quinazolines synthesis

After Rossi s synthesis of quinazolines via 6 7T-electrocyclization (see Scheme 2), a few but unique quinazoline synthesis by electrocyclization were reported [202,203]. On the other hand, rapid analogue synthetic methods of substituted l,2,3-triazolo[l,5-a]quinazolines based on cycloaddition/conden-sation of 2-azidobenzoic acid or related compounds were developed by... 

A particularly interesting example of this method of synthesis is the cy-clrzation of the 4-amino-3-(2-aminophyenyl)-l,2,4-triazoloes 73 with cyanogen bromide. Primarily, this reaction was applied to synthesize the 6-amino-l,2,4-triazolo[4,3-d]benzodiazepine hydrobromides 74 the obtained products, however, were found to be the l,5-diamino-l,2,4-triazolo-[l,5-c]quinazolin-ium bromides 77. Structure elucidation of 77 was accomplished by direct... 

In one synthesis [76JAP(K)76100098], l,2,4-triazolo[4,3-a]quinazolines (304) were prepared from 1,2,4-triazole precursors when 2-(l, 2,4-triazol-3-yl)benzophenones (303, LG = OR,SH, or SR) were cyclized with ammonia. 

Synthesis of l,2,4-triazolo[l,5-c]quinazolines from nonquinazoline intermediates is also known. Thus, the two heterocyclic rings were formed by the reaction of acylhydrazines with 2-ureidobenzonitriles (89JPR-537), 2-ethoxycarbonylaminobenzonitriles (329) (87USP4713383), or 2-isocyanatobenzonitrile (87CZ373) to give the title compounds (e.g. 330). 

Synthesis of 9-substituted tetrahydroazepinopurines as asmarine analogs has been described <03T6493>. In relation to adenosine receptor antagonists, new derivatives of pyrazolo[4,3-c][l,2,4]triazolo[l,5-c]pyrimidines have been synthesized <03IMC1229, 4287>. A one-pot synthesis of l,2,4-triazolo[l,5-c]quinazoline thiones 65, consisting of a domino cyclization of 2-isothiocyanatobenzonitrile 63 with hydrazides 64 has been published <03EJO182>. 

To add a synthesis chosen from the triazoloquinazoline series, the reaction of the activated aryl chloride 2,3-dichloro-6-nitrobenzonitrile and 3-methylthio AT leads to a mixture of isomeric triazolo[5,l-b]- and triazolo[l,5-a]quinazoline derivatives, though both in poor yields (95JHC1359). 

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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