New Synthesis of Pyrazolo[3,4‐b][1,4,5]benzothiadiazepine, ‐[1,4,5]benzoxadiazepine, ‐[1,4,5]benzotriazepine and Pyrazolo[3,4‐b]quinoxaline Derivatives

Abstract

New pyrazolo[3,4‐b][1,4,5]benzothiadiazepine and its analogues 3 have been obtained by reaction of 4‐nitrosopyrazoles 1 with 2‐aminothiophenol 2a and its analogues 2b,c. Under fused conditions, dipyrazolyl derivatives 7a was obtained with a trace amount of quinoxaline 5a. On the other hand, 5b and 7b were obtained in equal amounts. A proposed pathway is presented.

Construction of pyrazole fused spiroketals by a (3 + 2) annulation reaction

“…Based on the experimental results and previous studies on 4-bromo pyrazolones, 3–7 a possible mechanism for this (3 + 2) annulation process was proposed (Scheme 4). Initially, under the basic condition, 4-bromo pyrazolone 1 and benzofuran-derived azadiene 2 undergo nucleophilic addition, followed by intramolecular nucleophilic substitution to give pyrazolone spiro three-membered cyclopropane intermediate C .…”

“…4 In 2004, El-Rady's group reported the nucleophilic addition/dehydration/cyclization/oxidative dehydrogenation cascade reaction between 4-bromo pyrazolone and 1,2-phenylenediamine to offer pyrazolo[3,4- b ]quinoxaline derivative. 5 Meanwhile, Chande's group achieved pyrazolo[5,4- d ]thiazoles in high yield via a cascade nucleophilic addition/dehydration/intramolecular thioheteronucleophilic substitution reaction of 4-bromo pyrazolones with amidinothiocarbamides. 6 In 2009, Eissa's group reported a ring closure reaction involving dehydration/dehydrobromination between 4-bromo pyrazolones with acetic acid azide of hydrazine derivatives, and the corresponding pyrazolo[4,3- e ]-1,3,4-oxadiazines were obtained in 69% and 73% yields, respectively.…”

“…Inspired by the previous work on the construction of fused pyrazole skeletons with 4-halopyrazolones 3–7 and benzofuran-derived azadienes 12 as substrates, it is envisaged to synthesize pyrazolone spiro three-membered cyclopropane intermediates from 4-bromo pyrazolones and benzofuran-derived azadienes through nucleophilic addition/cyclization reaction, followed by ring cleavage/ring reconstruction to obtain pyrazole fused spiroketals. That is, the (3 + 2) annulation reaction occurs to realize the construction of pyrazole derivatives containing both fused pyrazole and spirocyclic skeleton in the molecule (Scheme 1b).…”

Elaboration of Benzoxadiazepine and Benzotriazocine Scaffolds

“…[29] After this publication, it was necessary to wait until 2002 for a renewed interest in these fused seven-membered heterocyles, with, in particular, the work of El Rady, focusing on diazonium salt reactivity. [30,31,32] The first strategy developed by El Rady was based on a one-pot reaction of nitrosoheteroaryls, easily obtained by nitrozation of cyanomethylheterocycles [30] or hydroxypyrazole derivatives, [31] with o-aminophenol as bisnucleophile. The ring closure was carried out under reflux of ethanol in the presence of trimethylamine or piperidine as base (Scheme 10).…”

Three‐Component Uncatalyzed Eco‐Friendly Reactions for One‐Pot Synthesis of 4,7‐Dihydro[1,2,4]triazolo[1,5‐a]pyrimidine Derivatives

“…Recently, the Biginelli reaction was developed for the synthesis of [1,2,4]triazolo [1,5-a]pyrimidine and its derivatives because of their remarkable diverse therapeutic and pharmacological activities such as analgesic, anticonvulsant, anti-inflammatory, antimalarials, antimicrobial, and antifungal effects [49][50][51][52]. Owing to the demand for an environmentally benign, green methodologies and continuing the interest for the synthesis of heterocyclic compounds [53][54][55][56][57][58], the synthesis of [1,2,4] triazolo [1,5-a]pyrimidine via a three-component system under reflux without any catalyst have been reported herein (Scheme 1).…”