Girijesh Verma | University of Delhi (original) (raw)
Papers by Girijesh Verma
Synlett, 2013
This feature focuses on a reagent chosen by a postgraduate, highlighting the uses and preparation... more This feature focuses on a reagent chosen by a postgraduate, highlighting the uses and preparation of the reagent in current research spotlight β-Oxodithioesters Compiled by Girijesh Kumar Verma Girijesh Kumar Verma was born in Deoria (India) in 1984. He received his B.Sc. (2005) and M.Sc. (2007) in Chemistry from Deen Dayal Upadhyay Gorakhpur University (India). He is currently pursuing his Ph.D. under the supervision of Professor M.
Tetrahedron Letters, Jan 25, 2012
A simple, efficient, and high yielding one-pot protocol for the synthesis of pyrimido[4,5-b]quino... more A simple, efficient, and high yielding one-pot protocol for the synthesis of pyrimido[4,5-b]quinolines and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidines has been developed by three-component domino coupling of 6-amino-1,3-dimethyluracil, aldehydes, and cyclic 1,3-diketones in ecofriendly solvent water promoted by PTSA. The protocol avoids the use of expensive catalysts, toxic solvents, and chromatographic separation. The generality and functional tolerance of this convergent and environmentally benign method is demonstrated.
A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones ha... more A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones has been developed by the cyclocondensation of ??-oxoketene dithioacetals and 2-hydroxyarylaldehydes catalyzed by InCl 3 under solvent-free conditions. No co-catalyst or ...
![Research paper thumbnail of A facile and highly convergent approach to thiazolo[3,2-a]pyridines via one-pot multicomponent domino reaction under metal-free and solvent-free conditions](https://attachments.academia-assets.com/43972817/thumbnails/1.jpg)
](Tetrahedron, 2015
One-pot domino reactions Solvent-free conditions Metal-free P 2 O 5 a b s t r a c t Operationally... more One-pot domino reactions Solvent-free conditions Metal-free P 2 O 5 a b s t r a c t Operationally and user-simple a highly efficient one-pot three-component (5 molecules) coupling of aenolic dithioesters, cysteamine hydrochloride and aldehydes afforded a range of thiazolopyridines in high yields under metal-free and solvent-free conditions. The new domino protocol generated two rings by the concomitant formation of seven multiple bonds (two CeC, three CeN and two CeS) involving a sequence of N,S-acetal formation/double Michael addition/N-cyclization as key steps in a single operation.
![Research paper thumbnail of ChemInform Abstract: Synthesis of N-Functionalized/NH-Multisubstituted Indoles, Thienopyrroles, Pyrroloindoles, and Pyrazolopyrroles via Sequential One-Pot Base-Mediated and Copper-Catalyzed Inter- and Intramolecular Amination of 2-[2-Bromo(het)aryl]-3-(h](https://attachments.academia-assets.com/44026096/thumbnails/1.jpg)
](ChemInform, 2015
A novel, efficient route to substituted 1-N-(het)aryl/NH-2-(het)aryl-3-cyanoindoles and related p... more A novel, efficient route to substituted 1-N-(het)aryl/NH-2-(het)aryl-3-cyanoindoles and related pyrrolo-fused heterocycles such as thienopyrroles, pyrroloindoles, and pyrazolopyrroles has been reported. The overall protocol involves sequential cycloamination of readily available 2-[2-bromo(het)aryl]-3-(het)aryl-3-(methylthio)acrylonitrile precursors with primary amines or amides via two key C−N bond-forming processes, one base-mediated intermolecular and the other Cucatalyzed intramolecular arylamination leading to N(1)−C(2) and N(1)−C(7a) bond formation, respectively, in a two-step onepot procedure.
Tetrahedron, 2011
A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2-thiones and benzo[f]2Hchr... more A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2-thiones and benzo[f]2Hchromene-2-thiones has been developed by the condensation of b-oxodithioesters and salicylaldehydes/ a-hydroxynaphthaldehydes in the presence of indium trichloride under solvent-free conditions. The reaction is operationally facile, readily scalable, and offers rapid entry into differentially substituted chromene-2-thione scaffolds.
RSC Advances, 2012
ABSTRACT
Tetrahedron Letters, 2011
Abstract A rapid and efficient one-pot three-component protocol for the synthesis of 2H-indazolo ... more Abstract A rapid and efficient one-pot three-component protocol for the synthesis of 2H-indazolo [2, 1-b] phthalazine-1, 6, 11-triones 4 and 1H-pyrazolo [1, 2-b] phthalazine-5, 10-diones 6 has been developed by domino coupling of phthalhydrazide, 1, 3-diketones, and ...
![Research paper thumbnail of ChemInform Abstract: Solvent-Free Sonochemical One-Pot Three-Component Synthesis of 2H-Indazolo[2,1-b]phthalazine-1,6,11-triones and 1H-Pyrazolo[1,2-b]phthalazine-5,10-diones](https://attachments.academia-assets.com/43972803/thumbnails/1.jpg)
](ChemInform, 2012
Solvent-Free Sonochemical One-Pot Three-Component Synthesis of 2H-Indazolo[2,1-b]phthalazine-1,6,... more Solvent-Free Sonochemical One-Pot Three-Component Synthesis of 2H-Indazolo[2,1-b]phthalazine-1,6,11-triones and 1H-Pyrazolo[1,2-b]phthalazine-5,10-diones. -The reaction under conventional heating or ultrasound gives the title compounds in comparable yields and reaction times. -(SHUKLA, G.; VERMA, R. K.; VERMA, G. K.; SINGH*, M. S.; Tetrahedron Lett. 52 (2011) 52, 7195-7198, http://dx.
ACS Combinatorial Science, 2012
A highly convergent and regioselective heteroannulation protocol for the synthesis of hitherto un... more A highly convergent and regioselective heteroannulation protocol for the synthesis of hitherto unreported highly substituted 2-amino-4-(aryl/alkyl)-5-(aroyl/heteroaroyl)-3-(cyano/carboalkoxy)-6-methylthio-4H-thiopyran derivatives has been developed. This one-pot three-component domino coupling of β-oxodithioesters, aldehydes, and malononitrile/ethyl or methyl cyanoacetate is promoted by 4-dimethylamino pyridine (DMAP) in solvent (dichloromethane (DCM)) as well as under solvent-free conditions. Systematic optimization of reaction parameters identified that the three-component coupling (3CC) protocol is tolerant to a wide array of functionality providing densely functionalized 4H-thiopyrans in excellent yields. The merit of this cascade Knoevenagel condensation/Michael addition/cyclization sequence is highlighted by its high atom-economy, excellent yields, and efficiency of producing three new bonds (two C-C and one C-S) and one stereocenter in a single operation.
RSC Advances, 2012
A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones ha... more A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones has been developed by the cyclocondensation of ??-oxoketene dithioacetals and 2-hydroxyarylaldehydes catalyzed by InCl 3 under solvent-free conditions. No co-catalyst or ...
Green Chem., 2015
A cost-effective and eco-friendly straightforward synthesis of highly diversified thiazoloquinoli... more A cost-effective and eco-friendly straightforward synthesis of highly diversified thiazoloquinoline scaffolds is successfully achieved via one-pot four-component cascade reaction utilizing α-enolic dithioesters, cysteamine, aldehydes, and cyclic 1,3-diketones in water-PEG-400. The new efficient domino protocol generates two rings by the concomitant formation of C-C (two), C-N (two), and C-S multiple bonds presumably involving a sequence of N,S-acetal formation, Knoevenagel reaction, aza-ene reaction, imineenamine/keto-enol tautomerization, and N-cyclization as key steps. The merit of this protocol is highlighted by its easily available and economical starting materials, operational simplicity, efficient utilization of all the reactants, clean reaction profile, simple workup procedure, and tolerance of a wide variety of functional groups. † This paper is dedicated to Prof. Ganesh Pandey on the occasion of his 60 th birthday. ‡ Electronic supplementary information (ESI) available: 1 H and 13 C NMR spectra of all compounds. CCDC 960941 (5ar), 1012571 (5ax) and 1012297 (5ba). For ESI and crystallographic data in CIF or other electronic format see a Reaction conditions: 1a (0.5 mmol) was treated with 2 (0.5 mmol) followed by addition of 3a (0.5 mmol) and 4a (0.5 mmol). b Total reaction time. c No reaction. d Reactants remained unconsumed.
ChemInform, 2014
An operationally simple and facile synthesis of a-hydroxyimino-b-oxodithioesters has been achieve... more An operationally simple and facile synthesis of a-hydroxyimino-b-oxodithioesters has been achieved by nitrosation of a-enolicdithioesters. They were further treated with internal alkynes to afford diverse 1,4thiazin-3-ones via domino reduction/annulation strategy under mild reaction conditions. Importantly, this is the first straightforward entry to highly functionalized 1,4-thiazin-3-one derivatives from simple starting materials.
ChemInform, 2014
An operationally simple and efficient approach to hitherto unreported and synthetically demanding... more An operationally simple and efficient approach to hitherto unreported and synthetically demanding 1,3-oxathiolan-2-ylidenes has been developed. The approach involves a cascade [2+3] heteroannulation of α-enolic dithioesters with epoxides promoted by non-nucleophilic moderate base Cs 2 CO 3 at room temperature. Typical features of this strategy include metal-free mild reaction conditions, atom-economy, high yields, and efficacy of forming two consecutive C-S and C-O bonds, and one ring in a single stroke. MeSH is the only by-product, and the stereochemistry of the exocyclic α-oxoketene moiety of 1,3-oxathiolane was assigned to have Zconfiguration.
Synlett, 2013
This feature focuses on a reagent chosen by a postgraduate, highlighting the uses and preparation... more This feature focuses on a reagent chosen by a postgraduate, highlighting the uses and preparation of the reagent in current research spotlight β-Oxodithioesters Compiled by Girijesh Kumar Verma Girijesh Kumar Verma was born in Deoria (India) in 1984. He received his B.Sc. (2005) and M.Sc. (2007) in Chemistry from Deen Dayal Upadhyay Gorakhpur University (India). He is currently pursuing his Ph.D. under the supervision of Professor M.
Tetrahedron Letters, Jan 25, 2012
A simple, efficient, and high yielding one-pot protocol for the synthesis of pyrimido[4,5-b]quino... more A simple, efficient, and high yielding one-pot protocol for the synthesis of pyrimido[4,5-b]quinolines and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidines has been developed by three-component domino coupling of 6-amino-1,3-dimethyluracil, aldehydes, and cyclic 1,3-diketones in ecofriendly solvent water promoted by PTSA. The protocol avoids the use of expensive catalysts, toxic solvents, and chromatographic separation. The generality and functional tolerance of this convergent and environmentally benign method is demonstrated.
A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones ha... more A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones has been developed by the cyclocondensation of ??-oxoketene dithioacetals and 2-hydroxyarylaldehydes catalyzed by InCl 3 under solvent-free conditions. No co-catalyst or ...
Tetrahedron, 2015
One-pot domino reactions Solvent-free conditions Metal-free P 2 O 5 a b s t r a c t Operationally... more One-pot domino reactions Solvent-free conditions Metal-free P 2 O 5 a b s t r a c t Operationally and user-simple a highly efficient one-pot three-component (5 molecules) coupling of aenolic dithioesters, cysteamine hydrochloride and aldehydes afforded a range of thiazolopyridines in high yields under metal-free and solvent-free conditions. The new domino protocol generated two rings by the concomitant formation of seven multiple bonds (two CeC, three CeN and two CeS) involving a sequence of N,S-acetal formation/double Michael addition/N-cyclization as key steps in a single operation.
ChemInform, 2015
A novel, efficient route to substituted 1-N-(het)aryl/NH-2-(het)aryl-3-cyanoindoles and related p... more A novel, efficient route to substituted 1-N-(het)aryl/NH-2-(het)aryl-3-cyanoindoles and related pyrrolo-fused heterocycles such as thienopyrroles, pyrroloindoles, and pyrazolopyrroles has been reported. The overall protocol involves sequential cycloamination of readily available 2-[2-bromo(het)aryl]-3-(het)aryl-3-(methylthio)acrylonitrile precursors with primary amines or amides via two key C−N bond-forming processes, one base-mediated intermolecular and the other Cucatalyzed intramolecular arylamination leading to N(1)−C(2) and N(1)−C(7a) bond formation, respectively, in a two-step onepot procedure.
Tetrahedron, 2011
A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2-thiones and benzo[f]2Hchr... more A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2-thiones and benzo[f]2Hchromene-2-thiones has been developed by the condensation of b-oxodithioesters and salicylaldehydes/ a-hydroxynaphthaldehydes in the presence of indium trichloride under solvent-free conditions. The reaction is operationally facile, readily scalable, and offers rapid entry into differentially substituted chromene-2-thione scaffolds.
RSC Advances, 2012
ABSTRACT
Tetrahedron Letters, 2011
Abstract A rapid and efficient one-pot three-component protocol for the synthesis of 2H-indazolo ... more Abstract A rapid and efficient one-pot three-component protocol for the synthesis of 2H-indazolo [2, 1-b] phthalazine-1, 6, 11-triones 4 and 1H-pyrazolo [1, 2-b] phthalazine-5, 10-diones 6 has been developed by domino coupling of phthalhydrazide, 1, 3-diketones, and ...
ChemInform, 2012
Solvent-Free Sonochemical One-Pot Three-Component Synthesis of 2H-Indazolo[2,1-b]phthalazine-1,6,... more Solvent-Free Sonochemical One-Pot Three-Component Synthesis of 2H-Indazolo[2,1-b]phthalazine-1,6,11-triones and 1H-Pyrazolo[1,2-b]phthalazine-5,10-diones. -The reaction under conventional heating or ultrasound gives the title compounds in comparable yields and reaction times. -(SHUKLA, G.; VERMA, R. K.; VERMA, G. K.; SINGH*, M. S.; Tetrahedron Lett. 52 (2011) 52, 7195-7198, http://dx.
ACS Combinatorial Science, 2012
A highly convergent and regioselective heteroannulation protocol for the synthesis of hitherto un... more A highly convergent and regioselective heteroannulation protocol for the synthesis of hitherto unreported highly substituted 2-amino-4-(aryl/alkyl)-5-(aroyl/heteroaroyl)-3-(cyano/carboalkoxy)-6-methylthio-4H-thiopyran derivatives has been developed. This one-pot three-component domino coupling of β-oxodithioesters, aldehydes, and malononitrile/ethyl or methyl cyanoacetate is promoted by 4-dimethylamino pyridine (DMAP) in solvent (dichloromethane (DCM)) as well as under solvent-free conditions. Systematic optimization of reaction parameters identified that the three-component coupling (3CC) protocol is tolerant to a wide array of functionality providing densely functionalized 4H-thiopyrans in excellent yields. The merit of this cascade Knoevenagel condensation/Michael addition/cyclization sequence is highlighted by its high atom-economy, excellent yields, and efficiency of producing three new bonds (two C-C and one C-S) and one stereocenter in a single operation.
RSC Advances, 2012
A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones ha... more A facile and efficient synthesis of 3-aroyl/heteroaroyl/ferrocenoyl/alkanoyl-2H-chromen-2-ones has been developed by the cyclocondensation of ??-oxoketene dithioacetals and 2-hydroxyarylaldehydes catalyzed by InCl 3 under solvent-free conditions. No co-catalyst or ...
Green Chem., 2015
A cost-effective and eco-friendly straightforward synthesis of highly diversified thiazoloquinoli... more A cost-effective and eco-friendly straightforward synthesis of highly diversified thiazoloquinoline scaffolds is successfully achieved via one-pot four-component cascade reaction utilizing α-enolic dithioesters, cysteamine, aldehydes, and cyclic 1,3-diketones in water-PEG-400. The new efficient domino protocol generates two rings by the concomitant formation of C-C (two), C-N (two), and C-S multiple bonds presumably involving a sequence of N,S-acetal formation, Knoevenagel reaction, aza-ene reaction, imineenamine/keto-enol tautomerization, and N-cyclization as key steps. The merit of this protocol is highlighted by its easily available and economical starting materials, operational simplicity, efficient utilization of all the reactants, clean reaction profile, simple workup procedure, and tolerance of a wide variety of functional groups. † This paper is dedicated to Prof. Ganesh Pandey on the occasion of his 60 th birthday. ‡ Electronic supplementary information (ESI) available: 1 H and 13 C NMR spectra of all compounds. CCDC 960941 (5ar), 1012571 (5ax) and 1012297 (5ba). For ESI and crystallographic data in CIF or other electronic format see a Reaction conditions: 1a (0.5 mmol) was treated with 2 (0.5 mmol) followed by addition of 3a (0.5 mmol) and 4a (0.5 mmol). b Total reaction time. c No reaction. d Reactants remained unconsumed.
ChemInform, 2014
An operationally simple and facile synthesis of a-hydroxyimino-b-oxodithioesters has been achieve... more An operationally simple and facile synthesis of a-hydroxyimino-b-oxodithioesters has been achieved by nitrosation of a-enolicdithioesters. They were further treated with internal alkynes to afford diverse 1,4thiazin-3-ones via domino reduction/annulation strategy under mild reaction conditions. Importantly, this is the first straightforward entry to highly functionalized 1,4-thiazin-3-one derivatives from simple starting materials.
ChemInform, 2014
An operationally simple and efficient approach to hitherto unreported and synthetically demanding... more An operationally simple and efficient approach to hitherto unreported and synthetically demanding 1,3-oxathiolan-2-ylidenes has been developed. The approach involves a cascade [2+3] heteroannulation of α-enolic dithioesters with epoxides promoted by non-nucleophilic moderate base Cs 2 CO 3 at room temperature. Typical features of this strategy include metal-free mild reaction conditions, atom-economy, high yields, and efficacy of forming two consecutive C-S and C-O bonds, and one ring in a single stroke. MeSH is the only by-product, and the stereochemistry of the exocyclic α-oxoketene moiety of 1,3-oxathiolane was assigned to have Zconfiguration.