Synthesis of a new tricylic ring system: [1,2,3]triazolo[1,5-b]cinnolinium salt

Abstract

Synthesis of the first representative of the linearly fused [1,2,3]triazolo [1,5-b]cinnolinium heteroaromatic cation as a quaternary salt is reported. Improved reaction conditions for preparation of some precursors have been elaborated. Reaction of the new heteroaromatic salt with nucleophiles resulted in regioselective formation of zwitterionic products.

A New Cyclization to Fused Pyrazoles Tunable for Pericyclic or Pseudopericyclic Route: An Experimental and Theoretical Study

“…Our literature survey indicated that similar ring closure with quinoxalines have been described: Boguslavskiy et al 21 described that treatment of 2-quinoxalylketone hydrazones with diluted sulfuric acid on air resulted in fused pyrazoles, whereas Sarodnick et al carried out similar ring closure in xylene at high temperature in the presence of chloranil. 22 In one of our recent publications, 23 we have reported on difficulties with transformation of 3-cinnolylketones (10) to hydrazones, and only the 4-nitrophenyl derivative (11) could be isolated. We have now found that with treatment of the majority of these ketones with arylhydrazines, a spontaneous ring closure to pyazolo[4,3-c]cinnolines (12) occurs (Scheme 4).…”

“…In one of our recent publications, we have reported on difficulties with transformation of 3-cinnolylketones ( 10 ) to hydrazones, and only the 4-nitrophenyl derivative ( 11 ) could be isolated. We have now found that with treatment of the majority of these ketones with arylhydrazines, a spontaneous ring closure to pyazolo[4,3- c ]cinnolines ( 12 ) occurs (Scheme ).…”

Syntheses and Applications of 1,2,3-Triazole-Fused Pyrazines and Pyridazines

“…Primary Applications : Use as highly conjugated linkers in triazole-based polymers [ 4 ] for the evaluation of solar cell materials is the main reported application. 1,2,3-Triazolo[1,5-b]pyridazines : The most common synthetic method is treatment of a keto-substituted pyridazine with p -bromophenyl hydrazine hydrochloride forming the hydrazone, then treatment with TBP in DCM [ 87 , 88 ]. A report of intramolecular cyclization of a diketo-oxime has been reported [ 86 ].…”

“…1,2,3-Triazolo[1,5-b]pyridazines : The most common synthetic method is treatment of a keto-substituted pyridazine with p -bromophenyl hydrazine hydrochloride forming the hydrazone, then treatment with TBP in DCM [ 87 , 88 ]. A report of intramolecular cyclization of a diketo-oxime has been reported [ 86 ].…”

“…This was followed by acidic workup to afford the desired ketone. Compounds of this type were also prepared by Vasko and coworkers [ 88 ] using a similar method, which gave a 27% yield. A third method for the synthesis of 1,2,3-triazolo[1,5- b ]pyridazines consisted of intramolecular oxidative ring closure of a hydrazone derived from 111 to afford the neutral 1,2,3-triazolo[1,5- b ]pyridazine 115 [ 89 ].…”