Regioselectivity in the multicomponent reaction of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal under controlled microwave heating

Abstract

SummaryThe multicomponent reaction of 5-aminopyrazole derivatives with cyclic 1,3-dicarbonyl compounds and dimethylformamide dimethylacetal (DMFDMA) in DMF at 150 °C under controlled microwave heating afforded regioselectively 8,9-dihydropyrazolo[1,5-a]quinazolin-6(7H)-ones 6 rather than the corresponding dihydropyrazolo[5,1-b]quinazolin-8(5H)-ones 4.

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

“…The preparation of a similar compound was indicated to proceed via two steps: Knoevenagel condensation between dimedone and aldehyde produced the adduct I , as a first step . The adduct I was subsequently reacted with aminopyrazole either at endocyclic NH or the exocyclic amino group followed by intramolecular cyclization through the loss of a water molecule to afford the linear tetrahydropyrazolo[5,1‐ b ]quinazolinone or angular tetrahydropyrazolo[5,1‐ b ]quinazolinone, respectively . However, Chebanov et al ruled out angular tetrahydropyrazolo[5,1‐ b ]quinazolinone, which would be formed by route B, as illustrated in (Figure ).…”

Microwave-assisted efficient one-pot synthesis of N 2-(tetrazol-5-yl)-6-aryl/heteroaryl-2,3-dihydro-1,3,5-triazine-2,4-diamines

“…Extensive efforts have been devoted to adopting green methodologies in synthetic heterocyclic chemistry. The utility of microwave heating technique as an energy source has several merits that include operational simplicity, high reaction yields, enhanced rates and increased energy efficiency [36][37][38][39][40][41][42].…”

A facile environment-friendly one-pot two-step regioselective synthetic strategy for 3,7-diarylpyrazolo[1,5-a]pyrimidines related to zaleplon and 3,6-diarylpyrazolo[1,5-a]pyrimidine-7-amines assisted by KHSO $$_{4}$$ 4 in aqueous media

“…For example, pyrazolo [1,5-a]pyrimidine derivatives have been prepared by reacting substituted 3(5)-aminopyrazoles with enaminones [11,18,19], enaminonitriles [20], β-ketoaldehydes [21], β-ketoesters [22], 1,3-diketones [23,24], sodium salts of formyl ketones [25], acetoacetanilides [26] and 3-oxo-2-phenylpropanenitrile [27] under acidic conditions (i.e., acetic acid, conc. HCl).…”

“…Other strategies involve the use of catalysts such as Mg-Al hydrotalcites [32], triethylamine [3], anhydrous zinc chloride [36] or under mild conditions without using any catalyst or promoter [37]. Microwave irradiation [23,32,35,38] has also been employed for the synthesis of pyrazolo[1,5-a]pyrimidine derivatives.…”