Richa Mohan

Alumina Catalyzed Synthesis of Fused Thioxopyrimidine Derivatives Under Microwaves

Abstract An expeditious solventless approach for the synthesis of pyrazolino[3,4-d]/isoxazolino[3,4-d]/pyrano[2,3-d]/iminopyrimidino[4,5-d]/thioxopyrimidino[4,5-d]/thiazino[5,4-d] pyrimidines from 2-thiobarbituric acid using supported reagents (acidic/basic alumina) under microwave irradiation (MWI) is described. The reaction times were brought down from hours to minutes with yield enhancement. Also the procedure highlights the versatility of solid supports.

A novel one pot synthesis of nitrogen containing heterocycles: an alternate methodology to the Biginelli and Hantzsch reactionsElectronic supplementary information (ESI) available: General procedure for the synthesis of Biginelli tetrahydropyrimidines (2b???e) and 1,4-dihydropyridines 3a???e. See http://www.rsc.org/suppdata/p1/b2/b205539m/

Modified Biginelli and Hantzsch reactions were carried using environmentally benign processes. Neat reactants subjected to microwave radiation gave the required products more quickly and in better yields in comparison to traditional methodologies. The observed yields and enhancement in reaction rates are due to the solvent free conditions coupled with the use of microwave radiation.

Environmentally benign synthesis of benzopyranopyrimidines

An ecologically benign method has been proposed for the synthesis of benzopyranopyrimidines by reaction of 4-hydroxycoumarins with aldehydes and urea or thiourea in the absence of a solvent under microwave irradiation. The proposed procedure improves the product yield and shortens the reaction time.

Solid-supported Hantzsch—Biginelli reaction for syntheses of pyrimidine derivatives

The microwave-assisted dry media technology was utilized for the synthesis of some novel derivatives in the Hantzsch—Biginelli reaction. In this eco-friendly approach, the usage of organic solvents and hazardous reagents resulting in corrossion of materials was minimized, giving high yields of products within a short reaction time.

A Novel Route to the Niementowski Reaction

The Niementowski reaction has been extended to synthesize 3-substituted/2,3-disubstituted4(3H)quinazolinones instead of the 2-substituted derivatives. The methodology is environmentally benign and completely eliminates the need of solvent from the reaction. Neat reactants were cyclocondensed under microwaves to afford, in good yield, the desired product in less irradiation time as compared to the classical technique. The reaction time was reduced from hours to minutes along with yield enhancement. The rate enhancement and high yield are attributed to the coupling of solvent-free conditions with microwaves.