Sangaraiah Nagarajan

Efficient synthesis and in vitro antitubercular activity of 1,2,3-triazoles as inhibitors of Mycobacterium tuberculosis

Efficient and rapid synthesis of 1,2,3-triazole derivatives has been achieved via Huisgens 1,3-dipolar cycloaddition between alkyl/arylazides and diethyl/dimethyl acetylenedicarboxylate in excellent yields under solvent-free conditions. The environmentally friendly solvent-free protocol overcomes the limitations associated with the prevailing time-consuming solution phase protocols and affords the triazoles just in 1-3 min. In vitro antitubercular activity of these triazoles was screened against Mycobacterium tuberculosis H(37)Rv strain. Four of the compounds showed MIC in the range of 1.56-3.13 μg/mL proving their potential activity.

The catalytic activity of titania nanostructures in the synthesis of amides under solvent-free conditions

Different shapes and phases of titania nanostructures with the uniform size distribution were synthesized by hydrothermal sol–gel technique. The influence of annealing temperature on the crystalline character, size and phase of the prepared nanomaterials were evidenced from the diffraction analysis. Infrared spectroscopic analysis ensured the structural confirmation of the sulfated titania nanostructures. Catalytic activity of the synthesized nanometric materials in direct amidation of aromatic and aliphatic carboxylic acids with aromatic amines was evaluated. Among the materials studied, sulfated titania nanotubes with the anatase phase exhibited excellent catalytic activity. The employed solvent-free protocol is greener and eradicates the drawbacks associated with the hazardous solvents employed in the prevailing solution phase methodologies.

An eco-friendly and water mediated product selective synthesis of 2-aminopyrimidines and their in vitro anti-bacterial evaluation

A greener water mediated protocol for the efficient synthesis of a library of 2-amino-6-styryl pyrimidines (4) and their dihydro analogues (3) has been reported. Most of the saturated compounds (3) rather than their unsaturated analogues (4) showed better anti-bacterial (in vitro) activity against three human pathogens viz. Staphylococcus aureus, Klebsiella pneumonia and Escherichia coli. In particular, three of them (3 b, 3 i &3 k) exhibited high inhibition against the growth of all the three pathogens comparable with that of the reference drug, tetracycline.

Microwave-assisted clean synthesis of amides via aza-wittig reaction under solvent-free condition

A solvent-free microwave-assisted coupling of phosphazenes with acyl chlorides or carboxylic anhydrides in presence of triethylphosphite has been accomplished resulting in a clean synthesis of amides in good yields. Unlike the prevailing time-consuming solution phase methodologies employing chlorinated solvents, benzene (carcinogenic), etc, the present protocol is an eco friendly, rapid and simple approach.

Water promoted one pot three-component synthesis of tetrazoles

A one pot, three component synthesis of tetrazoles via thiourea has been accomplished in water. Water enhances the solubility of a higher number of components in the three component protocol thus promoting the reaction. The synthesis involves a chemoselective exocyclic reaction, regioselective electrocyclisation and a preferred conformational orientation of the tetrazole side chain which are rationalised based on the relative magnitude of Garbisch angle strain/allylic strains anticipated during the course of the reaction.

A facile synthesis of 1,2,3-triazolyl indole hybrids via SbCl3-catalysed Michael addition of indoles to 1,2,3-triazolyl chalcones

AbstractAn efficient, facile and environmentally benign synthesis of a library of 1,2,3-triazolyl chalcone hybrids (3a–u) has been accomplished by grinding the reactants at room temperature in excellent yields in very short reaction time. Subsequently, SbCl3 catalysed Michael addition of indoles to the chalcones afford 1,2,3-triazolyl indole hybrids (5a–l) in excellent yields. Graphical AbstractAn efficient, facile and environmentally benign synthesis of a library of 1,2,3-triazolyl chalcone hybrids (3a–u) has been accomplished by grinding the reactants at room temperature in excellent yields in very short reaction times. Subsequently, SbCl3 catalysed Michael addition of indoles to the chalcones afforded 1,2,3-triazolyl indole hybrids (5a–l) in excellent yields.

A facile, rapid, one-pot regio/stereoselective synthesis of 2-iminothiazolidin-4-ones under solvent/scavenger-free conditions.

Summary A rapid and efficient one pot solvent/scavenger-free protocol for the synthesis of 2-iminothiazolidin-4-ones has been developed. Interestingly, the regio/stereoselective synthesis affords the regioisomeric (Z)-3-alkyl/aryl-2-(2-phenylcyclohex-2-enylimino)thiazolidin-4-one as the sole product in good yield. The selectivities observed have been rationalized based on the relative magnitude of the allylic strains developed during the course of the reaction. This is the first report wherein the impact of allylic strains in directing the regiocyclization has been noted.

Chemoselectivity in Coupling of Azides with Thioacids in Solution-Phase and Solvent-Free Conditions

Abstract Solvent-free rapid coupling of monothiocarboxylic acid with azide affords carboxamide chemoselectively. Triphenyl phosphine included as an additive influences the chemoselectivity, yielding carboxamide and thioamide. Similar variation in the chemoselectivity is observed in the absence and presence of triphenyl phosphine in solution-phase methodology. Rapidity and ecofriendliness of the solvent-free approach to yield the products in just 15 min is noteworthy compared to the solution-phase protocol, which has a long reaction time (1–3 days). GRAPHICAL ABSTRACT

CRYSTAL STRUCTURE AND DFT STUDIES OF 4-(1-BENZYL-5-METHYL-1H-1,2,3-TRIAZOL-4-YL)-6-(3- METHOXYPHENYL)PYRIMIDIN-2-AMINE

The title compound 1, 4-(1-benzyl-5-methyl-1H-1,2,3-triazol-4-yl)-6-(3-methoxyphenyl)pyrimidin-2-amine (C 21 H 20 N 6 O), was synthesized and structurally characterized by elemental analysis, 1H NMR, 13C NMR and single crystal X-ray diffraction. The molecular conformation is stabilized by an intramolecular C–H…N hydrogen bond, which generates an S(6) ring motif. In the crystal, molecules are linked by two pairs of inversion-related amine N-H N and C-H N hydrogen bonds, each generating alternate R 2 2(8) ring motifs in a zigzag supramolecular chain that runs along c-axis. These chains stack along a-axis via amine N-H…O hydrogen bonds forming a two-dimensional supramolecular network. Density functional theory calculations of the structure, Mulliken population analyses on atomic charges and thermodynamic functions of the title compound were performed by using (DFT/B3LYP) method with the 6-311G(d,p) basis set level. The charge energy distribution and site of chemical reactivity of molecules were obtained by mapping electron density isosurface with electrostatic potential surfaces. The thermo dynamical properties of the title compound at different temperature have been calculated and corresponding relations between the properties and temperature have also been obtained. 1,2,3-triazoles found to have wide range of important applications in the pharmaceutical, polymer, and material fields 1. In addition, they have shown a broad spectrum of biological properties such as anti-bacterial2 anti-allergic3, anti-HIV activity4 and also serve as potential chemotherapeutic agents for various diseases5. On the other hand, substituted pyrimidine nuclei are found antiviral6, anti-tubercular, antineoplastic, anti-inflammatory, diuretic, antimalarial and cardiovascular7. In view of these bioactivities of the individual heterocycles, it was envisaged that the synthesis of novel hybrid molecules containing two of the above said moieties in a single frame is worth to attempt. Literature survey reveals that so for there is no experimental and theoretical study for the title compound. In recent years, density functional theory (DFT) has become an increasingly useful tool for theoretical studies. The success of DFT is mainly due to the fact that it describes small molecules more reliably than Hartree-Fock theory. It is also computationally less demanding than wave function based methods with inclusion of electron correlation8-9. Thus, in order to characterize the correlation between molecular structure and macroscopic properties in the studied compound, it seems to be essential to undertake a detailed comparative study of the isolated molecule and the solid state unit. In this paper, a concerted approach by X-ray crystallography and DFT calculation was used, which takes advantage of both the high interpretative power of the theoretical studies and the precision and reliability of the experimental method. The title compound has been synthesized and antibacterial activities are reported by our co-authors10. In this paper, we report the synthesis, crystal structure of 4-(1-benzyl-5-methyl-1H-1,2,3-triazol-4-yl)-6-(3-methoxyphenyl) pyrimidin-2-amine (C 21 H 20 N 6 O), as well as theoretical studies using the DFT(B3LYP) method and 6-311G(d,p) basis set. The aim of the present work was to describe and characterize the molecular structure and some electronic structure properties of the title compound, both experimentally and theoretically. Also, chemical reactivity values such as chemical hardness, chemical potential electronegativity and electrophilicity index and HomoLumo energy gap obtained theoretically can be used to understand the biological activity of the title compound.