Rathinam Ramesh

PEG-assisted two-component approach for the facile synthesis of 5-aryl-1,2,4-triazolidine-3-thiones under catalyst-free conditions

A straightforward and greener PEG-assisted protocol has been disclosed for the facile synthesis of 5-aryl-1,2,4-triazolidine-3-thiones via the two-component reaction of multifarious aromatic aldehydes and thiosemicarbazides using very convenient neutral reaction conditions. This methodology represents a sustainable approach for rapid access to a library of diversity-oriented highly pure triazolidine scaffolds with broad substrate scope.

Synthesis of pyran annulated heterocyclic scaffolds: a highly convenient protocol using dimethylamine

A facile and rapid three-component synthesis of pharmaceutically diverse pyran annulated heterocycles has been developed via a one-pot condensation of aromatic aldehydes, malononitrile, and different enolizable C–H-activated acidic compounds in the presence of dimethylamine as a newer and effective organo-catalyst in ethanol under mild reaction conditions. Selectivity of various pyran derivatives depends on the structure of enolates. The present protocol has synthetic advantages of excellent yields in much shorter reaction times with no chromatography.

Glycerol assisted eco-friendly strategy for the facile synthesis of 4,4'-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ols) and 2-aryl-2,3-dihydroquinazolin-4(1H)-ones under catalyst-free conditions

This article describes glycerol mediated eco-friendly approaches for the convenient access of structurally diverse 4,4′-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ol) and 2-aryl-2,3-dihydroquinazolin-4(1H)-one motifs under catalyst-free conditions. Prominent advantages include clean processes, atom-efficiency, simplicity of the work-up, neutral conditions, low-cost reaction medium, excellent product yield and solvent reusability, in addition to relatively shorter reaction times.Graphical Abstract

Click and facile access of substituted tetrahydro-4H-chromenes using 2-aminopyridine as a catalyst

A highly convenient and greener method for the facile synthesis of pharmaceutically diverse 2-amino-5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles via a one-pot, three component condensation of aromatic aldehydes, malononitrile, and 1,3-cyclohexanedione or dimedone using 2-aminopyridine as an efficient alkaline organo catalyst is described. This new chemistry furnishes the desired heterocycles in very shorter reaction times with higher purity and has the advantages of economic viability, ease of preparation, excellent yields, and recyclability of catalyst.Graphical Abstract

Catalyst-free one-pot synthesis and antioxidant evaluation of highly functionalized novel 1,4-dihydropyridine derivatives

A catalyst-free greener protocol for the most effective one-pot synthesis of 2,6-diamino-4-aryl-1-propyl/cyclohexyl-1,4-dihydropyridine-3,5-dicarbonitrile derivatives has been developed using a simple three-component reaction of structurally diverse aldehydes, malononitrile and n-propylamine/cyclohexylamine at an ambient temperature. The formation of 1,4-dihydropyridines could be achieved in aqueous methanol in a single synthetic process involving no chromatography. The newly synthesized highly functionalized 1,4-DHPs have been screened for their in vitro antioxidant activity using the DPPH radical scavenging technique and the results were good in comparison with a standard drug.

Carbon–SO 3 H derived from glycerol: a green recyclable catalyst for synthesis of 2,3-dihydroquinazolin-4(1 H )-ones

In this study, we have described a clean and facile condensation reaction of various aromatic aldehydes or cyclic ketones with 2-aminobenzamide under mild conditions in the presence of C–SO3H as an efficient catalyst derived from glycerol. This protocol furnishes an imperative avenue for the access of 2,3-dihydroquinazolin-4(1H)-ones in excellent yields with a range of structural diversity. The recovered catalyst has been engineered for subsequent runs with substantial activity.Graphical Abstract

One-pot synthesis of symmetrical and unsymmetrical acridine sulfonamide derivatives catalyzed by p-TSA

Synthesis of a series of symmetrical and unsymmetrical 1,8-dioxo-octahydroacridine benzenesulfonamide derivatives has been achieved by one-pot, multicomponent reaction of aromatic aldehydes and sulfanilamide with cyclic 1,3-dicarbonyl compounds by using p-toluenesulfonic acid as an effective, cheap, and efficient catalyst. Reaction progress was monitored by thin-layer chromatography (TLC), and products were analyzed by Fourier-transform infrared (FT-IR), 1H and 13C nuclear magnetic resonance (NMR), and mass spectroscopy (MS).Graphical Abstract

Ceric Ion Loaded MCM-41 Catalyzed Synthesis of Substituted Mono- and Bis-dihydropyrimidin-2(1H)-ones

An effective one-pot three-component reaction of aromatic aldehydes with 1,3-diketone and urea or thiourea under solvent-free condition leads to the formation of mono- and bis-dihydropyrimidin-2-(1H)-ones using Ce-MCM-41 as a recyclable solid acid catalyst. This method has several advantages like simple and easy work-up with shorter reaction time, reusability of catalyst, and high yields of Biginelli products.

An Organocatalytic Newer Synthetic Strategy Toward the Access of Polyfunctionalized 4H-Pyrans via Multicomponent Reactions

GRAPHICAL ABSTRACT ABSTRACT An energy efficient, facile, and environmentally benign synthetic method to obtain pharmaceutically fortunate, diverse 4H-pyrans from frequently accessible aryl aldehydes, malononitrile, and dissimilar 1,3-diketoesters is described. The reactions took place smoothly at ambient temperature using 2-aminopyridine as a low-cost organocatalyst. The present domino strategy furnishes, the desired products in high yields with shorter reaction times. The structures of the o-nitro substituted skeletons were unambiguously confirmed by mono-crystal XRD.

CCDC 1493110: Experimental Crystal Structure Determination

Related Article: Rathinam Ramesh, Raji Madhesh, Jan Grzegorz Malecki, Appaswami Lalitha|2016|Chem. Sel.|1|5196|doi:10.1002/slct.201601358