A new convenient synthesis of 2,4‐disubstituted‐1,2,4‐triazolo[1,5‐a] quinazolin‐5(4H)‐ones

Synthesis of New 3,7,9-Trisubstituted Pyrazolo[4,3-e][1,2,4]Triazolo[4,3-c] Pyrimidines Acyclo C-Nucleosides via Oxidative Cyclisation

“…For example, several 3-and/or 5-substituted-7H-pyrazolo [4,3-e] [1,2,4] triazolo [4,3-c]pyrimidines and the isomeric pyrazolo [4,3- e] [1,2,4]triazolo [1,5-c]pyrimidine ring system possess one of the structural requirements for compounds that behave as selective antagonists for human A 2A and A 3 adenosine receptor subtypes. 11 As a result of these findings and in continuation of our previous work on the synthesis of fused triazoles, [12][13][14][15][16] we report herein the synthesis of 3,7,9-trisubstituted pyrazolo [4,3-e] [1,2,4]triazolo [4,3-c] pyrimidines, namely, 3-substituted-7,9diphenyl pyrazolo [4,3-e] [1,2,4]triazolo [4,3-c]pyrimidine acyclo C-nucleosides via tandem generation and 1,5-electrocyclisation of their respective C-(1-alditolyl)N- (1,3-diphenylpyrazolo[3,4-d] pyrimidin-4-yl)nitrilimines which have been hitherto unreported.…”

Design and synthesis of novel quinazolinone-based derivatives as EGFR inhibitors with antitumor activity

“…Compounds 1a,b were then treated with hydrazine hydrate 99% as reported to yield 2-hydrazinyl-3-phenylquinazolin-4( 3H )-one ( 2a ) and 3–(4-chlorophenyl)-2-hydrazinylquinazolin-4( 3H )-one ( 2b ) 31 . Furthermore, heating the obtained hydrazine derivatives 2a,b with 4-substituted benzaldehyde derivatives in ethanol as solvent in the presence of few drops of glacial acetic acid 42 afforded the novel target compounds 3a–g . The 1 H NMR spectra of the compounds 3a–g showed D 2 O exchangeable singlet signal due to NH at the range δ 10.49–10.61 ppm.…”

Bis-enaminones as precursors for synthesis of novel 3,4-bis(heteroaryl)pyrazoles and 3,6-bis-(heteroaryl)-pyrazolo[3,4-d]pyridazines

“…Also, its 1 H NMR spectrum did not show a signal characteristic of a -CHO group, they it exhibited two characteristic singlet signals at δ 7.87and 8.58 assignable to H-3 and H-5 of the [1,2,4]triazolo [3,4-c] [1,2,4]triazine ring residue, respectively. 12 To account for the formation of 8, it is suggested (Scheme 3), that the initially formed azo coupled product A can either undergo in situ cyclisation via elimination of dimethylamine to give 8 or hydrolysis to give the bis-aldehyde derivative B which in turn undergoes dehydrative cyclisation to afford 8. 13,14 However, when the diketone 8 was refluxed with hydrazine hydrate for 2 h the product was identified as the pyrazolopyridazine 9.…”

“…This rearrangement is compatible with those reported in earlier reports on rearrangements of [1,2,4] triazolo [3,4-c] [1,2,4]triazines and pyrimidines. 12,15 Conclusive evidence for the rearrangement of 9 into 10, was provided by comparison of their 1 H NMR spectra. For example, the 1 H NMR spectrum of 9 revealed the H-3 proton signal at δ 8.88, whereas that of 10 showed the H-7 proton signal at δ 8.47.…”