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Maya Shankar Singh - One of the best experts on this subject based on the ideXlab platform.
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Switching Selectivity of α-Enolic Dithioesters: One Pot Access to Functionalized 1,2- and 1,3-Dithioles
Journal of Organic Chemistry, 2016Co-Authors: Suvajit Koley, Subhasis Samai, Tanmoy Chanda, Maya Shankar SinghAbstract:An operationally simple cascade protocol has been developed for the construction of 1,2- and 1,3-dithiole derivatives from α-enolic Dithioesters. 1,2-Dithioles are achieved by the reaction of Dithioesters with elemental sulfur in the presence of InCl3 under solvent-free conditions. 1,3-Dithioles have been constructed via DABCO mediated self-coupling of Dithioesters in open air enabling the formation of two new C–S bonds and one ring in a single operation in contiguous fashion. The reactions proceeded smoothly affording the desired sulfur-rich heterocycles in good to excellent yields, exhibiting gram-scale ability and broad functional group tolerance utilizing easy to handle cheap and easily available reagents. The probable mechanisms for the formation of 1,2- and 1,3-dithioles from α-enolic Dithioesters have been suggested.
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Acid-Controlled Chemodivergent Synthesis of Three Differently Substituted Quinolines via Site Selective Coupling of ortho- Aminoaryl Ketones with α-Enolic Dithioesters
Advanced Synthesis & Catalysis, 2016Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Maya Shankar SinghAbstract:A straightforward approach for the chemodivergent synthesis of quinolines is described through site-selective coupling of ortho-aminoaryl ketones with α-enolic Dithioesters (DTEs) under solvent-free conditions. The operationally and user-simple one-pot methodology is based on the trifunctional nature of DTEs. Both the carbonyl and the thiocarbonyl moiety in α-enolic Dithioesters were employed for the efficient construction of three differently substituted quinolines in a chemoselective manner simply by variation of an easy to handle acid catalyst.
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Iron-Promoted Domino Annulation of α-Enolic Dithioesters with Ninhydrin under Solvent-Free Conditions: Chemoselective Direct Access to Indeno[1,2-b]thiophenes.
ChemInform, 2015Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Ganesh Chandra Nandi, Maya Shankar SinghAbstract:The title reaction of ninhydrin with Dithioesters gives condensed thiophenes in high yields.
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In/I2 mediated functional group transformation: a direct approach toward the selective conversion of Dithioester to ester
Tetrahedron Letters, 2015Co-Authors: Sushobhan Chowdhury, Suvajit Koley, Tanmoy Chanda, Maya Shankar SinghAbstract:Abstract A facile, direct approach for the selective conversion of Dithioester to ester functional group has been developed. In/I2 in methanol efficiently promotes the interesting functional group transformation at room temperature. Applying the newly developed mild conditions, a series of α-allyl-β′-oxoDithioesters have been converted to the corresponding α-allyl-β′-oxoesters in moderate to good yields. Interestingly, during the transformation the Dithioester groups of the starting α-allyl-β′-oxoDithioesters are selectively transformed to the corresponding methyl esters while the other functionalities within the moiety remained unaffected; hence requires no cumbersome protection–deprotection during the synthetic transformation.
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Ligand‐ and Base‐Free CuII‐Mediated Selective S‐Arylation of α‐Enolic Dithioesters by Chan–Lam Coupling at Room Temperature
European Journal of Organic Chemistry, 2014Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Namrata Anand, Maya Shankar SinghAbstract:The ligand- and base-free copper(II)-mediated Chan–Lam cross-coupling of arylboronic acids with α-enolic Dithioesters has been achieved at room temperature under aerobic neutral conditions to afford unsymmetrical α-oxoketene S,S-acetals for the first time. This operationally simple, mild protocol tolerates a wide range of arylboronic acids and α-enolic Dithioesters. Typical features of this novel strategy include short reaction times (5 min), good yields and highly selective C=S functionalization leading to S-arylation in one pot.
Suvajit Koley - One of the best experts on this subject based on the ideXlab platform.
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Switching Selectivity of α-Enolic Dithioesters: One Pot Access to Functionalized 1,2- and 1,3-Dithioles
Journal of Organic Chemistry, 2016Co-Authors: Suvajit Koley, Subhasis Samai, Tanmoy Chanda, Maya Shankar SinghAbstract:An operationally simple cascade protocol has been developed for the construction of 1,2- and 1,3-dithiole derivatives from α-enolic Dithioesters. 1,2-Dithioles are achieved by the reaction of Dithioesters with elemental sulfur in the presence of InCl3 under solvent-free conditions. 1,3-Dithioles have been constructed via DABCO mediated self-coupling of Dithioesters in open air enabling the formation of two new C–S bonds and one ring in a single operation in contiguous fashion. The reactions proceeded smoothly affording the desired sulfur-rich heterocycles in good to excellent yields, exhibiting gram-scale ability and broad functional group tolerance utilizing easy to handle cheap and easily available reagents. The probable mechanisms for the formation of 1,2- and 1,3-dithioles from α-enolic Dithioesters have been suggested.
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Acid-Controlled Chemodivergent Synthesis of Three Differently Substituted Quinolines via Site Selective Coupling of ortho- Aminoaryl Ketones with α-Enolic Dithioesters
Advanced Synthesis & Catalysis, 2016Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Maya Shankar SinghAbstract:A straightforward approach for the chemodivergent synthesis of quinolines is described through site-selective coupling of ortho-aminoaryl ketones with α-enolic Dithioesters (DTEs) under solvent-free conditions. The operationally and user-simple one-pot methodology is based on the trifunctional nature of DTEs. Both the carbonyl and the thiocarbonyl moiety in α-enolic Dithioesters were employed for the efficient construction of three differently substituted quinolines in a chemoselective manner simply by variation of an easy to handle acid catalyst.
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Iron-Promoted Domino Annulation of α-Enolic Dithioesters with Ninhydrin under Solvent-Free Conditions: Chemoselective Direct Access to Indeno[1,2-b]thiophenes.
ChemInform, 2015Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Ganesh Chandra Nandi, Maya Shankar SinghAbstract:The title reaction of ninhydrin with Dithioesters gives condensed thiophenes in high yields.
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In/I2 mediated functional group transformation: a direct approach toward the selective conversion of Dithioester to ester
Tetrahedron Letters, 2015Co-Authors: Sushobhan Chowdhury, Suvajit Koley, Tanmoy Chanda, Maya Shankar SinghAbstract:Abstract A facile, direct approach for the selective conversion of Dithioester to ester functional group has been developed. In/I2 in methanol efficiently promotes the interesting functional group transformation at room temperature. Applying the newly developed mild conditions, a series of α-allyl-β′-oxoDithioesters have been converted to the corresponding α-allyl-β′-oxoesters in moderate to good yields. Interestingly, during the transformation the Dithioester groups of the starting α-allyl-β′-oxoDithioesters are selectively transformed to the corresponding methyl esters while the other functionalities within the moiety remained unaffected; hence requires no cumbersome protection–deprotection during the synthetic transformation.
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Ligand‐ and Base‐Free CuII‐Mediated Selective S‐Arylation of α‐Enolic Dithioesters by Chan–Lam Coupling at Room Temperature
European Journal of Organic Chemistry, 2014Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Namrata Anand, Maya Shankar SinghAbstract:The ligand- and base-free copper(II)-mediated Chan–Lam cross-coupling of arylboronic acids with α-enolic Dithioesters has been achieved at room temperature under aerobic neutral conditions to afford unsymmetrical α-oxoketene S,S-acetals for the first time. This operationally simple, mild protocol tolerates a wide range of arylboronic acids and α-enolic Dithioesters. Typical features of this novel strategy include short reaction times (5 min), good yields and highly selective C=S functionalization leading to S-arylation in one pot.
Tanmoy Chanda - One of the best experts on this subject based on the ideXlab platform.
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Switching Selectivity of α-Enolic Dithioesters: One Pot Access to Functionalized 1,2- and 1,3-Dithioles
Journal of Organic Chemistry, 2016Co-Authors: Suvajit Koley, Subhasis Samai, Tanmoy Chanda, Maya Shankar SinghAbstract:An operationally simple cascade protocol has been developed for the construction of 1,2- and 1,3-dithiole derivatives from α-enolic Dithioesters. 1,2-Dithioles are achieved by the reaction of Dithioesters with elemental sulfur in the presence of InCl3 under solvent-free conditions. 1,3-Dithioles have been constructed via DABCO mediated self-coupling of Dithioesters in open air enabling the formation of two new C–S bonds and one ring in a single operation in contiguous fashion. The reactions proceeded smoothly affording the desired sulfur-rich heterocycles in good to excellent yields, exhibiting gram-scale ability and broad functional group tolerance utilizing easy to handle cheap and easily available reagents. The probable mechanisms for the formation of 1,2- and 1,3-dithioles from α-enolic Dithioesters have been suggested.
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Acid-Controlled Chemodivergent Synthesis of Three Differently Substituted Quinolines via Site Selective Coupling of ortho- Aminoaryl Ketones with α-Enolic Dithioesters
Advanced Synthesis & Catalysis, 2016Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Maya Shankar SinghAbstract:A straightforward approach for the chemodivergent synthesis of quinolines is described through site-selective coupling of ortho-aminoaryl ketones with α-enolic Dithioesters (DTEs) under solvent-free conditions. The operationally and user-simple one-pot methodology is based on the trifunctional nature of DTEs. Both the carbonyl and the thiocarbonyl moiety in α-enolic Dithioesters were employed for the efficient construction of three differently substituted quinolines in a chemoselective manner simply by variation of an easy to handle acid catalyst.
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Iron-Promoted Domino Annulation of α-Enolic Dithioesters with Ninhydrin under Solvent-Free Conditions: Chemoselective Direct Access to Indeno[1,2-b]thiophenes.
ChemInform, 2015Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Ganesh Chandra Nandi, Maya Shankar SinghAbstract:The title reaction of ninhydrin with Dithioesters gives condensed thiophenes in high yields.
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In/I2 mediated functional group transformation: a direct approach toward the selective conversion of Dithioester to ester
Tetrahedron Letters, 2015Co-Authors: Sushobhan Chowdhury, Suvajit Koley, Tanmoy Chanda, Maya Shankar SinghAbstract:Abstract A facile, direct approach for the selective conversion of Dithioester to ester functional group has been developed. In/I2 in methanol efficiently promotes the interesting functional group transformation at room temperature. Applying the newly developed mild conditions, a series of α-allyl-β′-oxoDithioesters have been converted to the corresponding α-allyl-β′-oxoesters in moderate to good yields. Interestingly, during the transformation the Dithioester groups of the starting α-allyl-β′-oxoDithioesters are selectively transformed to the corresponding methyl esters while the other functionalities within the moiety remained unaffected; hence requires no cumbersome protection–deprotection during the synthetic transformation.
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Ligand‐ and Base‐Free CuII‐Mediated Selective S‐Arylation of α‐Enolic Dithioesters by Chan–Lam Coupling at Room Temperature
European Journal of Organic Chemistry, 2014Co-Authors: Suvajit Koley, Tanmoy Chanda, Sushobhan Chowdhury, B. Janaki Ramulu, Namrata Anand, Maya Shankar SinghAbstract:The ligand- and base-free copper(II)-mediated Chan–Lam cross-coupling of arylboronic acids with α-enolic Dithioesters has been achieved at room temperature under aerobic neutral conditions to afford unsymmetrical α-oxoketene S,S-acetals for the first time. This operationally simple, mild protocol tolerates a wide range of arylboronic acids and α-enolic Dithioesters. Typical features of this novel strategy include short reaction times (5 min), good yields and highly selective C=S functionalization leading to S-arylation in one pot.
A Rosowsky - One of the best experts on this subject based on the ideXlab platform.
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1,2-Dithiol-3-thione and Dithioester analogues: potential radioprotectors
British Journal of Cancer, 1990Co-Authors: Ba Teicher, J Stemwedel, Ts Herman, Pk Ghoshal, A RosowskyAbstract:Several 1,2-dithiol-3-thione and Dithioester compounds were assayed for radioprotective capabilities in EMT6 cells in vitro. The 1,2-dithiol-3-thiones were generally more cytotoxic than the Dithioesters and in some instances were more cytotoxic toward hypoxic cells than toward normally oxygenated cells. When the drugs were present at a concentration of 500 microM for 1 h prior to and during radiation delivery, the 5-(2-thienyl)-1,2-dithiol-3-thione produced a radiation protection factor (RPF) of 2.7 at 1 log of cell kill. The 4-methyl analogue of this same compound was, however, much less effective, producing a RPF of only 1.2. The 4-ethoxycarbonyl analogue was moderately active, producing a RPF of 1.7. The 4-methyl-5-(2-pyrazinyl)-1,2-dithiol-3-thione (Oltipraz) was least effective, yielding a RPF of only 1.1. Of the Dithioesters tested, methyl 3-pyrrolidino-2-phenylpropene dithiocarboxylate produced a RPF of 2.6, methyl 3-piperidino-2-phenylpropenedithiocarboxylate a RPF of 2.7, and the corresponding 3-morpholino and 3-thiomorpholino derivatives RPF values of 2.7 and 2.9, respectively. The iodide salt of 4-ethoxycarbonyl-5-(2-thienyl)-1,2-dithiol-3-thione produced a RPF of 2.6 Methyl 3-cyclohexylamino-2-phenylpropenedithiocarboxylate was equally effective (RPF = 2.6). Finally, methyl 3-morpholino-3-thienyl-2-methylpropenedithiocarboxylate and methyl 3-morpholino-3-(2-pyrazinyl)-2-methylpropenedithiocarboxylate were less effective, producing RPF values of 2.0 and 1.6, respectively. These results demonstrate that several of these compounds are highly effective radioprotectors. In vitro and in vivo studies testing their efficacy are underway.
Jean-marc Corpart - One of the best experts on this subject based on the ideXlab platform.
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Use of Original ω‐Perfluorinated Dithioesters for the Synthesis of Well‐Controlled Polymers by Reversible Addition‐Fragmentation Chain Transfer (RAFT)
Macromolecular Chemistry and Physics, 2002Co-Authors: Pierre Lebreton, Bruno Ameduri, Bernard Boutevin, Jean-marc CorpartAbstract:A series of five fluorinated Dithioesters PhC(S)SRCH 2 C n F 2n+1 (where R represents an activating spacer and n= 6 or 8) was obtained in fair to high yields (57-88%). These transfer agents were successfully used in reversible addition-fragmentation transfer (RAFT) of styrene (S), methyl methacrylate (MMA), ethyl acrylate (EA) and 1,3-butadiene. Well-chosen fluorinated Dithioesters were able to lead to a good control of the radical polymerization of these monomers (i.e., molar masses of the produced polymers increased linearly with the monomer conversion and the polydispersity indexes ranging between 1.1 and 1.6 remained low). The relationship between the structures of the Dithioesters and the living behavior of the radical polymerization of these above monomers is discussed and it is shown that the nature of the R group influences the living behavior from different contributions to radical stabilization. Furthermoren the RAFT process alos yielded PMMA-b-PS and PEA-b-PS block copolymers bearing a fluorinated moiety.