Studies with Alkylheteroaromatic Carbonitriles: A Novel Synthesis of Pyrazolo[2′,3′: 3,4]benzo[c]-1,2,4-triazine

Abstract

A novel synthesis of derivatives of the title ring system by reacting methylpyrazolo[5,1-c]-1,2,4-triazin-6-carbonitriles (9) with sulphur and subsequent treatment of the resulting thienopyrazolotriazines with acetivated double bond system is described.

Non-aromatic azolo[5,1-c][1,2,4]triazines: a pot, atom and step economic (PASE) synthesis, mechanistic insight and fluorescence properties

“…The latter can be cyclized either through formyl derivatives B (in the presence of water) formed through the elimination of a dimethylamine fragment or directly due to its cleavage, which leads to the formation of aromatic products C . 3,9…”

“…Consideration of the literature data on the interaction of diazoazoles or azole diazonium salts with enamines, showed that the published discussions about the mechanisms of these interactions, as well as the conclusions drawn, are not supported by the experimental data. [3][4][5][6][7][8][9][10] We collected all the proposed pathways and main intermediates and they are shown in Scheme 2. The first of the proposed hypotheses considers the formation of azolo[5,1-c][1,2,4]triazines C as a result of a C-azo coupling reaction of the C-2 of the activated double bond of enamines with the corresponding diazonium salts to afford azo intermediates A.…”

“…The first of the proposed hypotheses considers the formation of azolo[5,1-c][1,2,4]triazines C as a result of a C-azo coupling reaction of the C-2 of the activated double bond of enamines with the corresponding diazonium salts to afford azo intermediates A. The latter can be cyclized either through formyl derivatives B (in the presence of water) formed through the elimination of a dimethylamine fragment or directly due to its cleavage, which leads to the formation of aromatic products C. 3,9 Another route is the dipolar cycloaddition and it is equally plausible because azoles with a diazo function are active dipoles. In this case, the aforementioned heterocyclic systems can be the result of an initial 1,3-5 or 1,7-cycloaddition.…”

“…This interaction is presented in several publications in the literature. 1–10 Azolo[5,1- c ][1,2,4]triazines and rarely α-(1,2,5-triazapenta-1,3-dienyl)azoles (azocompounds) 10 have been isolated in low to moderate yields as the main products of this reaction. Non-aromatic dihydropyrazolo[5,1- c ][1,2,4]triazines were declared to be intermediates in the 1,7- or 1,3-cycloaddition pathways.…”

“…This interaction is presented in several publications in the literature. [1][2][3][4][5][6][7][8][9][10] Azolo [5,1-c] [1,2,4]triazines and rarely a-(1,2,5triazapenta-1,3-dienyl)azoles (azocompounds) 10 have been isolated in low to moderate yields as the main products of this reaction.…”