Microwave-assisted synthesis of fused pyrazolo[3,4-b]pyrazines by the reaction of ortho-aminonitrosopyrazoles and cyclic β-diketones

Microwave-Assisted Synthesis of Bioactive Six-Membered Heterocycles and Their Fused Analogues

“…Mechanistic study of the isoquinolines synthesis reported by Alfonsi et al [233] Scheme 56. Mechanistic study of the isoquinolines synthesis reported by Alfonsi et al [233] Derivatives of 2(1H)-pyrazinones are considered as important scaffolds for drug design due to their widespread biological activities [234][235][236][237][238][239]. In this context, Gising et al [237] have reported a rapid and versatile one-pot MW-assisted two steps synthesis of N-1 and C-6 functionalized 3,5-dichloro-2(1H)-pyrazinones 258.…”

“…In the second step, the expected pyrazinones are obtained through the cyclocondensation of the α-aminonitrile with oxalyl chloride in the presence of gaseous HCl in 1,2-dimethoxyethane; this second step occurs also under MW-irradiation (Scheme 57). An original synthetic route to pyrazolo [3,4-b]pyrazine derivatives 261 has been described by Quiroga et al [239], which proceeds through a MW-induced cyclocondensation of ortho-aminonitrosopyrazoles 259 and cyclic β-diketones 260 in DMF through an extension of the Ehrlich-Sachs reaction (Scheme 58). According to the authors' hypothesis, the reaction is initiated by chemo-selective addition of the enol tautomer of the diketone to the nitroso group of the pyrazole, resulting in formation of an imine.…”

“…their widespread biological activities [234][235][236][237][238][239]. In this context, Gising et al [237] have reported a rapid and versatile one-pot MW-assisted two steps synthesis of N-1 and C-6 functionalized 3,5-dichloro-2(1H)-pyrazinones 258.…”

“…Scheme 59. Mechanistic study of the pyrazolo [3,4-b]pyrazines synthesis reported by Quiroga et al [239]. Oxazine derivatives are also considered as important pharmacophores in drug discovery ( Figure 16).…”

Synthesis, Anti-inflammatory and Antibacterial Activities of Novel Pyrazolo[4,3-<i>g</i>]pteridines

“…1,2) Their synthesis has increased noticeably in recent years owing to their diverse biological activities such as antimicrobial and antiparasitic ones. [3][4][5] In continuation to our research work on the synthesis of new pyrazole-based heterocycles with potential biological activities as antimicrobial, [6][7][8][9][10][11][12] as anticonvulsant, 13,14) as β 1 -adrenergic blocking agents, 15) we wish to report herein the synthesis of some novel pyrazolo [4,3-g] pteridines and evaluating their anti-inflammatory and antibacterial activities. bered lactone and also showed the disappearance of absorption bands of the acidic OH and NH 2 groups and that refers to its involvement in the cyclization process.…”