A four-component reaction: regio- and chemoselective formation of 7-amino-2-(tert-butyl)-5-aryl-4,5-dihydropyrazolo[1,5-a]pyrimidine-6-carbonitrile

Bicyclic 5-6 Systems: Comprehensive Synthetic Strategies for the Annulations of Pyrazolo[ 1,5-a]pyrimidines

Pyrazolopyrimidines are a privileged class of 5-6 bicyclic systems with three or four nitrogen atoms, including four possible isomeric structures. The significance of this class of compounds is that they can be applied in medical and pharmaceutical fields due to their unlimited biological aptitude, hence it is the basic skeleton of several synthetic drugs. The current review aimed to highlight all the synthetic routes that have been applied to construct the pyrazolo[1,5-a]pyrimidine ring systems up to date. The sections in this study included the synthesis of pyrazolo[1,5- a]pyrimidines by condensation reactions of 5-aminopyrazoles with each of β-diketones, 1,5-diketones, β- ketoaldehydes, α-cyanoaldehydes, β-enaminones, enamines, enaminonitriles, ethers, with unsaturated ketones, unsaturated thiones, unsaturated esters, unsaturated dienones "1,2-allenic", unsaturated aldehydes, unsaturated imines, and unsaturated nitriles. The routes adopted to synthesize this class of heterocyclic compounds were extended for ring construction from acyclic reagents and multicomponent reactions under catalytic or catalyst-free conditions.

Solvent-free synthesis of isoindolo[2,1-c]pyrazolo[1,5-a]quinazoline and pyrazolo[5',1':2,3]pyrimido[6,1-a]isoindol derivatives through a one-pot three-component reaction

Some 5-substituted 3-aminopyrazoles were used for the synthesis of isoindolo[2,1-c]pyrazolo[1,5-a]quinazoline and pyrazolo[5',1':2,3]pyrimido[6,1-a]isoindol derivatives via a mild and efficient one-pot three-component reaction with 2-formylbenzoic acid and different CH-acids under solvent-free condition.