Synthesis of isomeric triazolopyrrolopyrimidines

Abstract

4‐Hydrazino‐7H‐pyrrolo[2,3‐d]pyrimidines (4) were cyclocondensed with formic acid or triethyl orthoformate to give 7H‐1,2,4‐triazolo[1,5‐c]pyrrolo[3,2‐e]pyrimidines (5) and 7H‐1,2,4‐triazolo[4,3‐c]pyrrolo‐[3,2‐e]pyrimidines (6) respectively. The [4,3‐c]‐isomers (6) were rearranged into thermodynamically more stable [1,5‐c]‐isomers (5). The identical compounds (5) were prepared using another route by reacting 3‐amino‐4‐imino‐7H‐pyrrolo[2,3‐d]pyrimidines (3) with formic acid or triethylorthoformate. Reaction of 2‐amino‐3‐cyanopyrroles (1) with triethyl orthoformate followed by hydrazinolysis afforded (3) via the formation of N‐ethoxymethylene‐2‐amino‐3‐cyanopyrroles (2).

Utility of thieno[2,3-b] pyridine derivatives in the synthesis of some condensed heterocyclic compounds with expected biological activity

“…Furthermore, compound 15 upon reaction with excess hydrazine hydrate [42] yielded novel pyridothienopyrimidine derivative 16. The reaction mechanism was reported [41] to be accomplished through addition of a hydrazine molecule on the enamine double bond followed by elimination of an ethanol molecule and intramolecular cyclization to yield the target compound 16.…”

Synthesis and antitumor evaluation of some new derivatives and fused heterocyclic compounds derived from thieno[2,3‐b]pyridine: Part 2

“…oxopyridine-3-carbonitrile derivative 30 in a mixture of acetic anhydride/pyridine [43] at 100°C furnished the corresponding pyrido [4,3-d]pyrimidine-4,5-dione derivative 31. [45] Additionally, the chlorinated compound 32 was also reacted with triethyl orthoformate in the presence of acetic anhydride [47] to afford the corresponding ethyl formimidate analogue 34 that was subjected to the hydrazinolysis via refluxing with an excess amount of hydrazine hydrate to yield 3-amino-5-chloro-4iminopyrimidine derivative [48] 35. [44] Chlorination of compound 30 was achieved via its treatment with phosphorus oxychloride containing few amounts of triethylamine as a catalyst [45] to afford the chlorinated product 32.…”

“…The latter intermediate underwent intramolecular cyclization via the addition of the hydrazinyl NH 2 function on the nitrile group. [45] Additionally, the chlorinated compound 32 was also reacted with triethyl orthoformate in the presence of acetic anhydride [47] to afford the corresponding ethyl formimidate analogue 34 that was subjected to the hydrazinolysis via refluxing with an excess amount of hydrazine hydrate to yield 3-amino-5-chloro-4iminopyrimidine derivative [48] 35. The chemical structures of both compounds were elucidated on the basis of their spectral and elemental analyses.…”

Synthesis of Some Novel Pyrido[2,3‐d]pyrimidine and Pyrido[3,2‐e][1,3,4]triazolo and Tetrazolo[1,5‐c]pyrimidine Derivatives as Potential Antimicrobial and Anticancer Agents

“…In our work on pyrido[2,3‐ d ]pyrimidines, we became interested to incorporate a triazol or tetrazol group in pyrimidine ring. The reason for this is that triazolo or tetrazolo derivatives are gaining importance because of their different and significant biological activities . The synthesis of pyridino[2,3‐ d ]pyrimidines is mainly by two ways, that is, annulations of pyrimidine ring over pyridine or vice versa .…”