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Papers by TWINKLE KESHARI
Green Chemistry, 2014
A mild, simple, efficient and metal-free approach to β-keto sulfoxides utilising eosin Y as an or... more A mild, simple, efficient and metal-free approach to β-keto sulfoxides utilising eosin Y as an organophotoredox catalyst has been developed. This general protocol offers a direct and rapid difunctionalization of alkenes using thiophenols and atmospheric oxygen at room temperature in a one-pot procedure. The utilisation of visible light and air (O2) as inexpensive, readily available, non-toxic and eco-sustainable reagents makes this protocol compatible with the green chemistry demands.
Synlett, 2014
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 Acid Hydrazides Compiled by Twinkle Keshari Twinkle Keshari was born in Mirjapur, Uttar Pradesh, India, in 1989. She received her B.Sc. (Hons) from Banaras Hindu University in 2010 and a M.Sc. from the University of Allahabad in 2012. Currently, she is pursuing her Ph.D. in the Department of Chemistry at the University of Allahabad under the supervision of Professor L. D. S. Yadav. Her research is focused on catalytic organic synthesis.
Tetrahedron Letters, Oct 1, 2015
The thiazole ring constitutes a broad spectrum of compounds useful in the field of agriculture an... more The thiazole ring constitutes a broad spectrum of compounds useful in the field of agriculture and medicinal chemistry. 1,2 Moreover, aminothiazole heterocycles have been explored as building blocks in organic synthesis and material science. 3 Aminothiazoles are also a privileged structural motif in numerous biologically active molecules. 4 They have been employed for the preparation of different important drugs required for the treatment of tuberculosis, 5a inflammations, 5a,6,7 allergies, 8 hypertension, 9 schizophrenia, 10 bacterial and HIV infections 5a,11-13 and human lymphatic filarial parasite (Fig. 1). 14 In addition, aminothiazoles are also known to be ligands of estrogen receptors as well as of adenosine receptor antagonists. 15 Analogs of aminothiazole have also agricultural importance for being used as fungicides. 16
Synlett, May 9, 2016
A convenient and efficient synthesis of symmetrical and asymmetric thiosulfonates from thiols and... more A convenient and efficient synthesis of symmetrical and asymmetric thiosulfonates from thiols and sodium sulfinates is reported. The protocol involves iron(III)-catalyzed formation of sulfenyl and sulfonyl radicals in situ under aerobic conditions and their subsequent cross-coupling to afford thiosulfonates in 83–96% yield. The utilization of readily available, nontoxic, and inexpensive iron(III) as a catalyst and atmospheric oxygen as an oxidant is within the confines of green and sustainable chemistry.
European Journal of Organic Chemistry, May 1, 2016
The first utilization of-nitrostyrenes (readily available by the Henry reaction) for a highly ste... more The first utilization of-nitrostyrenes (readily available by the Henry reaction) for a highly stereoselective, convenient, and catalytic synthesis of (E)-vinyl sulfones at room temperature was investigated. The protocol involves efficient silver-[a] Green Synthesis Lab,
ChemInform, Sep 1, 2016
Silver-Catalyzed Denitrative Sulfonylation of -Nitrostyrenes: A Convenient Approach to (E)-Vinyl... more Silver-Catalyzed Denitrative Sulfonylation of -Nitrostyrenes: A Convenient Approach to (E)-Vinyl Sulfones.-The utilization of -nitrostyrenes (readily available by the Henry reaction) for a highly stereoselective, convenient, and catalytic synthesis of (E)-vinyl sulfones at room temperature is investigated. The protocol involves efficient silver-catalyzed denitrative radical cross-coupling of -nitrostyrenes and sodium sulfinates by using potassium persulfate as an additive to complete the catalytic cycle.-(
ChemInform, 2016
Thio compounds Q 0590 Carbon Tetrabromide Mediated Carbon-Sulfur Bond Formation via a Sulfenyl Br... more Thio compounds Q 0590 Carbon Tetrabromide Mediated Carbon-Sulfur Bond Formation via a Sulfenyl Bromide Intermediate.-A new route to sulfur-containing products includes the reaction of active methylenes or indole with the sulfur components in the presence of CBr4 and base, with the formation of sulfenyl bromide as a key step.-(TAN, J.;
Synlett
A photocatalytic [3+2] cycloaddition of aziridines with activated alkynes is reported under visib... more A photocatalytic [3+2] cycloaddition of aziridines with activated alkynes is reported under visible-light irradiation in the presence of ruthenium catalyst. This chemical transformation provides polysubstituted pyrrolidines in good yields based on the click chemistry philosophy. The reaction successfully represents a primary trial of cyclocarboamination through photocascade catalysis combining energy transfer and redox neutral reactions.
Tetrahedron Letters, 2017
Visible light triggered regioselective ring expansion of N-tosylaziridines: an efficient approach... more Visible light triggered regioselective ring expansion of N-tosylaziridines: an efficient approach to 2-nitroazetidines
Org. Biomol. Chem., 2014
General information ii. General procedure iii. Spectroscopic and analytical data for compounds 3 ... more General information ii. General procedure iii. Spectroscopic and analytical data for compounds 3 and 4 iv. References v. NMR spectra of products 3 and 4 i. General information: Reagents were obtained from commercial suppliers, and used without further purification. Organic solutions were concentrated using a Buchi rotary evaporator. Column chromatography was carried out over silica gel (Merck 100-200 mesh) and TLC was performed using silica gel GF254 (Merck) plates. 1 H NMR spectra were recorded on a Bruker AVII 400 spectrometer in CDCl 3 using TMS as internal reference with chemical shift value being reported in ppm. All coupling constants (J) are reported in hertz (Hz). 13 C NMR spectra were recorded on the same instrument at 100 MHz in CDCl 3 and TMS was used as internal reference. Mass (EI) spectra were recorded on a JEOL D-300 mass spectrometer. Elemental analyses were carried out in a Coleman automatic analyzer.
Green Chemistry, 2014
A mild, simple, efficient and metal-free approach to β-keto sulfoxides utilising eosin Y as an or... more A mild, simple, efficient and metal-free approach to β-keto sulfoxides utilising eosin Y as an organophotoredox catalyst has been developed. This general protocol offers a direct and rapid difunctionalization of alkenes using thiophenols and atmospheric oxygen at room temperature in a one-pot procedure. The utilisation of visible light and air (O2) as inexpensive, readily available, non-toxic and eco-sustainable reagents makes this protocol compatible with the green chemistry demands.
Synlett, 2014
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 Acid Hydrazides Compiled by Twinkle Keshari Twinkle Keshari was born in Mirjapur, Uttar Pradesh, India, in 1989. She received her B.Sc. (Hons) from Banaras Hindu University in 2010 and a M.Sc. from the University of Allahabad in 2012. Currently, she is pursuing her Ph.D. in the Department of Chemistry at the University of Allahabad under the supervision of Professor L. D. S. Yadav. Her research is focused on catalytic organic synthesis.
Tetrahedron Letters, Oct 1, 2015
The thiazole ring constitutes a broad spectrum of compounds useful in the field of agriculture an... more The thiazole ring constitutes a broad spectrum of compounds useful in the field of agriculture and medicinal chemistry. 1,2 Moreover, aminothiazole heterocycles have been explored as building blocks in organic synthesis and material science. 3 Aminothiazoles are also a privileged structural motif in numerous biologically active molecules. 4 They have been employed for the preparation of different important drugs required for the treatment of tuberculosis, 5a inflammations, 5a,6,7 allergies, 8 hypertension, 9 schizophrenia, 10 bacterial and HIV infections 5a,11-13 and human lymphatic filarial parasite (Fig. 1). 14 In addition, aminothiazoles are also known to be ligands of estrogen receptors as well as of adenosine receptor antagonists. 15 Analogs of aminothiazole have also agricultural importance for being used as fungicides. 16
Synlett, May 9, 2016
A convenient and efficient synthesis of symmetrical and asymmetric thiosulfonates from thiols and... more A convenient and efficient synthesis of symmetrical and asymmetric thiosulfonates from thiols and sodium sulfinates is reported. The protocol involves iron(III)-catalyzed formation of sulfenyl and sulfonyl radicals in situ under aerobic conditions and their subsequent cross-coupling to afford thiosulfonates in 83–96% yield. The utilization of readily available, nontoxic, and inexpensive iron(III) as a catalyst and atmospheric oxygen as an oxidant is within the confines of green and sustainable chemistry.
European Journal of Organic Chemistry, May 1, 2016
The first utilization of-nitrostyrenes (readily available by the Henry reaction) for a highly ste... more The first utilization of-nitrostyrenes (readily available by the Henry reaction) for a highly stereoselective, convenient, and catalytic synthesis of (E)-vinyl sulfones at room temperature was investigated. The protocol involves efficient silver-[a] Green Synthesis Lab,
ChemInform, Sep 1, 2016
Silver-Catalyzed Denitrative Sulfonylation of -Nitrostyrenes: A Convenient Approach to (E)-Vinyl... more Silver-Catalyzed Denitrative Sulfonylation of -Nitrostyrenes: A Convenient Approach to (E)-Vinyl Sulfones.-The utilization of -nitrostyrenes (readily available by the Henry reaction) for a highly stereoselective, convenient, and catalytic synthesis of (E)-vinyl sulfones at room temperature is investigated. The protocol involves efficient silver-catalyzed denitrative radical cross-coupling of -nitrostyrenes and sodium sulfinates by using potassium persulfate as an additive to complete the catalytic cycle.-(
ChemInform, 2016
Thio compounds Q 0590 Carbon Tetrabromide Mediated Carbon-Sulfur Bond Formation via a Sulfenyl Br... more Thio compounds Q 0590 Carbon Tetrabromide Mediated Carbon-Sulfur Bond Formation via a Sulfenyl Bromide Intermediate.-A new route to sulfur-containing products includes the reaction of active methylenes or indole with the sulfur components in the presence of CBr4 and base, with the formation of sulfenyl bromide as a key step.-(TAN, J.;
Synlett
A photocatalytic [3+2] cycloaddition of aziridines with activated alkynes is reported under visib... more A photocatalytic [3+2] cycloaddition of aziridines with activated alkynes is reported under visible-light irradiation in the presence of ruthenium catalyst. This chemical transformation provides polysubstituted pyrrolidines in good yields based on the click chemistry philosophy. The reaction successfully represents a primary trial of cyclocarboamination through photocascade catalysis combining energy transfer and redox neutral reactions.
Tetrahedron Letters, 2017
Visible light triggered regioselective ring expansion of N-tosylaziridines: an efficient approach... more Visible light triggered regioselective ring expansion of N-tosylaziridines: an efficient approach to 2-nitroazetidines
Org. Biomol. Chem., 2014
General information ii. General procedure iii. Spectroscopic and analytical data for compounds 3 ... more General information ii. General procedure iii. Spectroscopic and analytical data for compounds 3 and 4 iv. References v. NMR spectra of products 3 and 4 i. General information: Reagents were obtained from commercial suppliers, and used without further purification. Organic solutions were concentrated using a Buchi rotary evaporator. Column chromatography was carried out over silica gel (Merck 100-200 mesh) and TLC was performed using silica gel GF254 (Merck) plates. 1 H NMR spectra were recorded on a Bruker AVII 400 spectrometer in CDCl 3 using TMS as internal reference with chemical shift value being reported in ppm. All coupling constants (J) are reported in hertz (Hz). 13 C NMR spectra were recorded on the same instrument at 100 MHz in CDCl 3 and TMS was used as internal reference. Mass (EI) spectra were recorded on a JEOL D-300 mass spectrometer. Elemental analyses were carried out in a Coleman automatic analyzer.