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Swaroop T.R.,University of Mysore | Ila H.,New Chemistry Unit | Rangappa K.S.,University of Mysore
Tetrahedron Letters | Year: 2013

An efficient, regioselective route to 2,4-bis(het)aryl-5(het)aroylthiazoles has been developed by cyclocondensation of thionyl chloride with novel β-(het)arylmethylaminoenones which are readily accessible by the reaction of (het)arylmethylamines with 1,3-bis(het)arylmonothio-1,3-diketones. The method allows entry to 2,4,5-trisubstituted thiazoles, with full control for the introduction of either a (het)aryl group at 2,4 positions or a (het)aroyl group at 5 position of the thiazole ring. © 2013 Elsevier Ltd. All rights reserved. Source


Swaroop T.R.,University of Mysore | Roopashree R.,University of Mysore | Ila H.,New Chemistry Unit | Rangappa K.S.,University of Mysore
Tetrahedron Letters | Year: 2013

A new regiospecific route to 2,4-disubstituted thiophenes has been developed through Simmon-Smith reaction on β-methylthio-α,β- unsaturated ketones. Extension of the reaction to β-ethyl/benzylthio- α,β-unsaturated ketones also gave the corresponding 2,4-disubstituted thiophenes in a regiospecific manner. A probable mechanism involving a carbenoid methylene insertion to divalent sulfur followed by intramolecular aldol condensation has been suggested. © 2012 Elsevier Ltd. All rights reserved. Source


Verma R.K.,Banaras Hindu University | Ila H.,New Chemistry Unit | Singh M.S.,Banaras Hindu University
Tetrahedron | Year: 2010

2-[Bis(methylthio)methylene]-1,3-indanedione has been shown to be a useful three carbon 1,3-dielectrophilic synthon for the highly efficient regiospecific synthesis of a variety of indenofused five- and six-membered heterocycles via heteroaromatic annulation. The methodology has been further elaborated to the corresponding N,S-acetals leading to amino substituted heterocycles, thus providing further point of diversity in the newly synthesized heterocyclic frameworks. Further, the facile access to cytotoxic indeno[2,1-c]quinolin-7-ones and the novel polycyclic heteroaromatics demonstrates the versatility of heteroaromatic annulation protocol via α-oxoketene-S,S-acetal in generating novel biologically important polycyclic heteroaromatics. © 2010 Elsevier Ltd. All rights reserved. Source


Lo S.-H.,Northwestern University | He J.,Northwestern University | He J.,Xian University of Science and Technology | Biswas K.,Northwestern University | And 3 more authors.
Advanced Functional Materials | Year: 2012

Transmission electron microscopy studies show that a PbTe-BaTe bulk thermoelectric system represents the coexistence of solid solution and nanoscale BaTe precipitates. The observed significant reduction in the thermal conductivity is attributed to the enhanced phonon scattering by the combination of substitutional point defects in the solid solution and the presence of high spatial density of nanoscale precipitates. In order to differentiate the role of nanoscale precipitates and point defects in reducing lattice thermal conductivity, a modified Callaway model is proposed, which highlights the contribution of point defect scattering due to solid solution in addition to that of other relevant microstructural constituents. Calculations indicate that in addition to a 60% reduction in lattice thermal conductivity by nanostructures, point defects are responsible for about 20% more reduction and the remaining reduction is contributed by the collective of dislocation and strain scattering. These results underscore the need for tailoring integrated lengtha scales for enhanced heata carrying phonon scattering in high performance thermoelectrics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Samai S.,Banaras Hindu University | Chanda T.,Banaras Hindu University | Ila H.,New Chemistry Unit | Singh M.S.,Banaras Hindu University
European Journal of Organic Chemistry | Year: 2013

An efficient and highly regioselective one-pot three-component synthesis of previously inaccessible and synthetically demanding 3-(cycloalkyl/alkyl/ arylamino)-5-aryl/alkylisoxazoles has been achieved by the cyclocondensation of β-oxo dithioesters, amines and hydroxylamine in ethanol at reflux. This transformation proceeds via an in situ generated β-oxothioamide by the reaction of the β-oxo dithioester and amine, which undergoes nucleophilic attack by hydroxylamine followed by intramolecular cyclization with the oxo functionality and subsequent dehydration to give 5-substituted 3-aminoisoxazoles as a single regioisomer in good yields. Furthermore, the mechanism of the reaction has been established experimentally and shown to be in agreement with the hard and soft (Lewis) acid and base (HSAB) theory. A highly regioselective synthesis of 5-substituted 3-aminoisoxazoles has been achieved by a one-pot three-component coupling of β-oxo dithioesters, amines and hydroxylamine in ethanol at reflux via an in situ generated β-oxo thioamide intermediate. The mechanism of the reaction has been established experimentally and shown to be in agreement with the HSAB theory. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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