Prasanta Gogoi

Grindstone chemistry: a highly efficient and green method for synthesis of 3,4-dihydropyrimidin-2-(1H)-ones by L-tyrosine as an organocatalyst: a combined experimental and DFT study

A single step, mild, environmentally friendly green method has been developed for the synthesis of physiologically active 3,4-dihydropyrimidin-2-(1H)-ones employing L-tyrosine as catalyst under solvent-free conditions at room temperature via grinding. The procedure is efficient, time saving and gives high-yields. The structures and purity of these compounds were confirmed by FT-IR, NMR (1H and 13C) and HRMS spectral analysis. DFT calculations have been used to show the effectiveness of L-tyrosine as a suitable catalyst for the above reaction.

Nickel(II), copper(II), and cobalt(II) complexes derived from a new unsymmetrical ONS donor Schiff base ligand: synthesis, characterization, crystal structure, and catalytic activities

Ni(II), Cu(II), and Co(II) complexes, ML2, with a new thioether containing ONS donors were synthesized, where L = deprotonated Schiff base. The analytical, spectral (FTIR, 1H NMR, and UV-vis), conductivity, and magnetic studies show that the metal complexes possess octahedral geometry and are non-electrolytes. The coordination mode of ligand, 1, and nickel(II) complex, NiL2, 2, was determined by single-crystal X-ray diffraction studies. Here, the nickel is coordinated to two oxygens, two nitrogens, and two sulfurs of two tridentate ligands with slightly distorted octahedral environment around nickel. The copper complex shows very good catalytic activities towards oxidation of organic thioethers to the corresponding sulfoxide predominantly using H2O2 as the oxidant. Graphical Abstract A series of Ni(II), Cu(II), and Co(II) complexes, ML2, of a new thioether containing ONS donors have been synthesized, where L = deprotonated Schiff base. The analytical, spectral (FTIR, 1H NMR, UV–vis), conductivity, and magnetic studies showed that the metal complexes possess octahedral geometry and are non-electrolytes. The structures of ligand as well as nickel(II) complex, NiL2, 2, were determined by single-crystal X-ray diffraction studies. The copper complex shows very good catalytic activities towards oxidation of organic thioethers to the corresponding sulfoxide predominantly using H2O2 as the oxidant.

TBATB mediated debenzylative cross-coupling of aryl benzyl sulfides with electron rich compounds: synthesis of diaryl sulfides

An efficient TBATB mediated debenzylative cross coupling of aryl benzyl sulfides with electron rich compounds provides diaryl sulfides in moderate to excellent yield. The salient features of the present protocol are simplicity, high efficiency and compatibility of the reaction with various electron rich compounds.

Role of TBATB in nano indium oxide catalyzed C-S bond formation.

Nano sized indium oxide is found to be an efficient catalyst for the conversion of thiols to sulfides using Na2CO3 as base and TBATB as reagent in DMSO at 110 °C. Here in situ generation of bromo intermediate by TBATB takes place through indium surface. A variety of aryl sulfides can be synthesized in excellent yields from less reactive chlorides, boronic acids and thiols.

Tetrabutylammonium tribromide impregnated MCM-48 as a heterogeneous catalyst for selective oxidation of sulfides

We report here tetrabutylammonium tribromide supported on MCM-48 as a highly efficient heterogeneous catalyst for the selective oxidation of sulfides, in ethanolic medium using hydrogen peroxide as an oxidant. The aforementioned oxidation reactions were found to proceed rapidly (20 min) and in good yield (85–99%) (17 examples). The oxidation products were characterized by 1H NMR, 13C NMR and elemental analysis. The catalytic properties were analysed by TEM, XRD and BET-surface area measurement. No over-oxidation of the substrates was observed (analysed by GC), and the catalyst was effectively recycled for five consecutive cycles without any significant loss in its catalytic activity.

Aluminium Chloride–Catalyzed Synthesis of 4-Benzyl Cinnolines from Aryl Hydrazones

Abstract An efficient synthesis of 4-benzyl cinnolines from aryl phenylallylidene hydrazone is described. In this report aluminium chloride as a Lewis acid catalyst and toluene as a solvent are used for the synthesis. This method is expected to more advantageous than the other reported methods of synthesis of the cinnoline rings because of its low cost, better yield, and benign reaction conditions. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Gold nanoparticle catalyzed intramolecular C–S bond formation/C–H bond functionalization/cyclization cascades

An efficient synthesis of 2-(N-aryl)aminobenzo[d]-1,3-thiazoles via intramolecular C–S bond formation/C–H bond functionalization utilizing an unusual cocatalytic Au-NPs/KMnO4 system under an oxygen atmosphere at 80 °C is presented. Au-NPs can be easily prepared by using HAuCl4 with reductive potential of Kayea assamica (sia nahor) aqueous fruit extract. The catalyst can be easily separated and recycled eight times without any appreciable loss of activity.

1-Benzoyl-3-[(2-benzylsulfanyl)phenyl]thiourea.

In the title compound, C(21)H(18)N(2)OS(2), a strong intramolecular N-H...O hydrogen bond [N...O = 2.642 (3) Å] between the amide N atom and the benzoyl O atom forms an almost planar six-membered ring in the central part of the molecule. In the crystal, molecules are packed through weak N-H...S interactions. Intra- and intermolecular hydrogen bonds and van der Waals interactions are the stabilizing forces for the crystal structure.

A novel dual-nano assisted synthesis of symmetrical disulfides from aryl/alkyl halides

Abstract Here, we have reported a novel approach towards dual-nano assisted synthesis of disulfides from coupling of alkyl/aryl halides and sulfur nanoparticles. The indium oxide nanoparticles as catalyst expedite the conversion and sulfur nanoparticle notably enhances the miscibility, providing a faster, high yielding and cost-effective process in ethanol-water system. The method has synthetic advantages in terms of mild reaction framework, catalyst regeneration, and absence of any sulfide or polysulfide linkage as by-product leading to a column free synthesis. A variety of alkyl, aryl and heteroaryl symmetrical disulfides are obtained in good to excellent yields up to exceeding 98%. Graphical Abstract