Subarna Jyoti Kalita

Reaction of 6-aminouracils with aldehydes in water as both solvent and reactant under FeCl3·6H2O catalysis: towards 5-alkyl/arylidenebarbituric acids

5-Alkyl/arylidenebarbituric acids were efficiently synthesized through an FeCl3·6H2O catalyzed domino reaction of 6-aminouracils, water and aldehydes with water serving a dual role as both solvent and reactant, under benign reaction conditions. A study on comparative substrate scope of 6-aminouracil versus barbituric acid showed similar efficacy towards 5-alkyl/arylidenebarbituric acids. The protocol is the first detailed report to prepare regioselectively 5-alkyl/arylidenebarbituric acids starting from 6-aminouracils, which is an alternative and competing strategy to hitherto all known reactions directly employing barbituric acids.

FeCl3·6H2O catalyzed aqueous media domino synthesis of 5-monoalkylbarbiturates: water as both reactant and solvent

A novel, simple and straightforward route to 5-monoalkylbarbiturates by FeCl3·6H2O catalyzed domino reactions of 6-aminouracils, water and α,β-unsaturated ketones, where water plays a key dual role as both reactant and solvent, is described. Significantly, all the reactions efficiently furnished exclusively 5-monoalkylbarbiturates and not pyrido[2,3-d]pyrimidines as generally produced from the reactions of 6-aminouracils and α,β-unsaturated carbonyls.

Organocatalytic domino Knöevenagel–Michael reaction in water for the regioselective synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines and pyrido[2,3-d]pyrimidin-2-amines

An organocatalyzed simple and general route towards the regioselective synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines and pyrido[2,3-d]pyrimidin-2-amines is developed via L-proline catalyzed domino reaction of 2-aminobenzimidazole or 2,6-diaminopyrimidin-4-one with aldehydes and β-ketoesters in water. High yields within a shorter reaction time, simple purification, and environmentally benign mild reaction conditions are the key features that make the protocol significantly applicable.

Ni–Al2O3 as reusable heterogeneous catalyst for expedient one-pot synthesis of naphthopyrans

Ni–Al2O3 is an efficient and reusable heterogeneous catalyst for the synthesis of naphthopyrans by one-pot three-component reaction of naphthols, aldehydes, and malononitrile in EtOH/H2O (1:1) solvent medium. A comparative study of Ni–Al2O3 with neutral Al2O3 revealed that reactions with the former afforded better product yields, indicating higher catalytic efficacy. Ni–Al2O3 due to its low cost, good activity, ease of handling, and easy recovery, with high yields and simple purification method makes the procedure highly applicable.Graphical Abstract

Expeditious synthesis of 2,3-dihydroquinazolin-4(1H)-ones in aqueous medium using thiamine hydrochloride (VB1) as a mild, efficient, and reusable organocatalyst

ABSTRACT A simple and straightforward synthesis of 2,3-dihydroquinazolin-4(1H)-ones is developed by reacting anthranilamide with various aldehydes or ketones under mild reaction conditions, using thiamine hydrochloride as a cost-effective, readily available, and green catalyst in water. Simple purification process, high yields within short reaction time, wide substrate scope, operational simplicity, and reusability of the catalyst up to three cycles enrich the applicability of the protocol. GRAPHICAL ABSTRACT