K. Logaiya

Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles using cellulose sulfuric acid as an efficient catalyst

A convenient approach to the synthesis of 2-amino-4,6-diphenylnicotinonitriles via four-component reaction of aromatic aldehydes, acetophenone derivatives, malononitrile and ammonium acetate is described. The reactions were done in water as solvent using cellulose sulfuric acid as catalyst. This simple protocol offer advantages such as shorter reaction times, simple work-up procedure, excellent yields and catalyst recovery.

Silica-supported perchloric acid (HClO4–SiO2): a mild, reusable and highly efficient heterogeneous catalyst for multicomponent synthesis of 1,4-dihydropyridines via unsymmetrical Hantzsch reaction

Facile synthesis of some 1,4-dihydropyridine derivatives via Hantzsch reaction of 5,5-dimethyl-1,3-cyclohexanedione (dimedone), 1,3-diphenyl-2-propen-1-one derivatives and ammonium acetate under solvent-free condition in the presence of silica-supported perchloric acid (HClO4–SiO2) is described. The catalyst is easily prepared, stable, reusable and efficient under the reaction conditions.

Reusable silica-bonded S-sulfonic acid catalyst for three-component synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes and 2-amino-4H-pyrans in aqueous ethanol

Silica-bonded S-sulfonic acid (SBSSA)-catalyzed, facile, one-pot, three-component coupling of 5,5-dimethyl-1,3-cyclohexanedione (dimedone) or 5,5-dimethyl-1,3-cyclohexanedione, aromatic aldehydes, and malononitrile at reflux temperature is described for preparation of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene derivatives. 2-Amino-3-cyano-6-methyl-4-phenyl-4H-pyran-5-ethylcarboxylate derivatives can also be prepared in good yield under the same experimental conditions by use of ethyl acetoacetate, aldehydes, and malononitrile. The catalyst, silica-bonded S-sulfonic acid, was reused and recycled without any loss of activity or product yield.

An appropriate one-pot synthesis of 3,4-dihydropyrano[c]chromenes and 6-amino-5-cyano-4-aryl-2-methyl-4H-pyrans with thiourea dioxide as an efficient, reusable organic catalyst in aqueous medium

Abstract An efficient, convenient method for the synthesis of 3,4-dihydropyrano[3,2-c]chromene derivatives by one-pot, three-component reaction of aldehydes, malononitrile/cyanoacetate, and 4-hydroxycoumarin in the presence of a catalytic amount of thiourea dioxide, an efficient, reusable organic catalyst, is described. A variety of 3,4-dihydropyrano[3,2-c]chromene derivatives were obtained, and 6-amino-5-cyano-4-phenyl-2-methyl-4H-pyran-3-carboxylic acid ethyl esters were obtained by condensation of aldehydes, malononitrile and ethyl acetoacetate in the presence of thiourea dioxide in aqueous medium. The salient features of the protocol are mild reaction conditions, high yields, short reaction time, safety, high atom-economy, eco-friendly standards, easy isolation of products, no column chromatographic separation and reusability of the catalyst.

An efficient one-pot synthesis of 1,4-dihydropyridine derivatives through Hantzsch reaction catalysed by melamine trisulfonic acid

Abstract The classical Hantzsch reaction is one of the simplest and most economical methods for the synthesis of biologically important and pharmacologically useful 1,4-dihydropyridine derivatives. Melamine trisulfonic acid (MTSA) under thermal condition is proven to act as a very efficient catalyst for a one-pot synthesis of 2-amino-4-phenyl-3-cyano-7,7-dimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline derivatives in excellent yields from aldehydes, dimedone, malononitrile and ammonium acetate under solvent-free conditions. The present environmentally benign procedure for the synthesis of 1,4-dihydropyridines is suitable for library synthesis and it will find application in the synthesis of potent biologically active molecules. The process presented here is operationally simple, environmentally benign and has excellent yield. Furthermore, the catalyst can be recovered conveniently and reused efficiently.

Aqua-mediated synthesis of acridinediones with reusable silica-supported sulfuric acid as an efficient catalyst

Abstract A simple approach to the synthesis of acridinediones via one-pot three-component condensation of an aromatic aldehyde, 5,5-dimethyl-1,3-cyclohexanedione (dimedone), and ammonium acetate or p-toluidine in water with use of silica-supported sulfuric acid as an efficient catalyst is described. Excellent yields, catalyst recovery and reusability, and easy work-up are attractive features of this green protocol. All the synthesized acridinediones were characterized on the basis of their melting-points, elemental analysis and spectral data.

Facile synthesis of 3,4-dihydropyrimidin-2(1H)-ones and -thiones and indeno[1,2-d]pyrimidines catalyzed by p-dodecylbenzenesulfonic acid

Abstract A facile method for synthesizing 3,4-dihydropyrimidin-2(1H)-ones and -thiones in the Biginelli reaction by condensation reaction of aldehydes, β-ketoesters and urea or thiourea with p-dodecylbenzenesulfonic acid as a recyclable catalyst under solvent-free conditions at 80 °C is described. A series of indeno[1,2-d]pyrimidines was also synthesized under the same conditions by a Biginelli-like reaction of 2H-indene-1,3-dione with urea or thiourea and an aromatic aldehyde. All the products in both reactions were obtained in good to excellent yield by this simple, efficient procedure. The structures of all the synthesized compounds were established from advanced spectroscopic data.