Iron(III) chloride catalysed three-component Grieco condensation: Synthesis of tetrahydropyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines/quinazolines

Microwave-Assisted Synthesis of Quinazolines and Quinazolinones: An Overview

Microwave irradiation (MWI), as a unique, effective, sustainable, more economic, and greener source of energy compared to conventional heating, is applied in different organic transformations to result in the rapid formation of desired compounds due to thermal/kinetic effects. In this review, we try to underscore the applications of microwave irradiation (MWI) in the synthesis of quinazoline and quinazolinone derivatives that have been achieved and reported on in the last two decades.

Synthesis of Pyrazolo[3,4-b]Pyridine and Pyrido[2′,3′:3,4]Pyrazolo [1,5-a]Pyrimidine Derivatives

The synthesis of two series of 1-phenyl and 1 H-pyrazolo[3,4- b]pyridine is described. Thus, reacting 5-amino-1-phenylpyrazole with chalcone analogues gave 4,6-diarylpyrazolo[3,4- b]pyridine derivatives. While, reacting the same starting material with benzylidene derivatives of ethyl cyanoacetate and malononitrile resulted in 4-oxo and 4-aminopyrazolo[3,4- b]pyridine derivatives, respectively. The synthesis of 3-amino-4,6-diarylpyrazolo[3,4- b]pyridines starting from pyridine was also described. Thus, chlorination of 4,6-diarylpyridone derivatives and their subsequent cyclisation with hydrazine hydrate afforded 3-amino-4,6-diarylpyrazolo[3,4 -b]pyridines. Reaction of the latter compounds with acetylacetone, ethyl ethoxymethylenecyanoacetate and chalcone analogue gave the tricyclic pyrido[2′,3′: 3,4]pyrazolo[1,5- a]pyrimidines. The structures of the products were confirmed by spectral data.

GdCl3 catalysed Grieco condensation: A facile approach for the synthesis of novel pyrimidine and annulated pyrimidine fused indazole derivatives in single pot under mild conditions and their anti-microbial activity

Indazole regioisomers such as 3-amino-4-(trifluoromethyl)-6-phenyl-1H-indazole-7-carbonitrile 1 and 3-amino-6-(trifluoromethyl)-4-phenyl-1H-indazole-7-carbonitrile 2 were independently reacted with formaldehyde followed by unsymmetrical, symmetrical and cyclic electron rich olefins in presence of GdCl(3) as catalyst and obtained pyrimidine fused indazole derivatives 3 and 4, respectively. The reaction is found to be concerted and an exclusive product is formed. Representative examples of compounds 3 and 4 were screened against Gram-positive, Gram-negative bacteria and fungal species such as yeast and filamentous fungi in vitro. Compound 3f showed significant activity against all species of Gram-positive and Gram-negative bacteria, whereas compounds 3h and 4a showed the least activity with reference to penicillin as well as streptomycin. Similarly compound 3c showed promising activity against yeast and filamentous fungi whereas compound 3f is inactive at the maximum concentration of 150 microg/mL.