The Experts below are selected from a list of 54 Experts worldwide ranked by ideXlab platform
Samir Z. Zard - One of the best experts on this subject based on the ideXlab platform.
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An expedient route to dihydrothiazines, a virtually unknown class of heterocycles.
Organic letters, 2013Co-Authors: Béatrice Quiclet-sire, Samir Z. ZardAbstract:Upon heating at 180-200 °C in diphenyl ether, S-(4-oximinoalkyl)xanthates with a secondary isopropyl or isobutyl group on the oxygen undergo a Chugaev Elimination followed by ring closure onto the oxime to give dihydrothiazines, a virtually unknown class of heterocycles.
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A Synthesis of (1E,3E)‑TMS Dienes from Keto-Xanthates via Chugaev‑Type Elimination
2013Co-Authors: Kelvin Kau Kiat Goh, Sunggak Kim, Samir Z. ZardAbstract:An efficient route leading to exclusively (1E,3E)-TMS dienes is described. Radical xanthate addition of keto-xanthates to vinyltrimethylsilane followed by one-pot Chugaev Elimination/cyclization and in situ oxidation with m-CPBA afforded the corresponding TMS 2-sulfolenes. Isomerization to 3-sulfolenes by the action of DBU with the extrusion of sulfur dioxide in refluxing toluene gave the titled (1E,3E)-TMS dienes
Samir Zard - One of the best experts on this subject based on the ideXlab platform.
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A Synthesis of (1E,3E)-TMS Dienes from Keto-Xanthates via Chugaev-Type Elimination
Journal of Organic Chemistry, 2013Co-Authors: Kelvin Kau Kiat Goh, Sunggak Kim, Samir ZardAbstract:An efficient route leading to exclusively (1E,3E)-TMS dienes is described. Radical xanthate addition of keto-xanthates to vinyltrimethylsilane followed by one-pot Chugaev Elimination/cyclization and in situ oxidation with m-CPBA afforded the corresponding TMS 2-sulfolenes. Isomerization to 3-sulfolenes by the action of DBU with the extrusion of sulfur dioxide in refluxing toluene gave the titled (1E,3E)-TMS dienes.
Bryan J Haugen - One of the best experts on this subject based on the ideXlab platform.
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An Approach to Cyclohepta[b]indoles through an Allenamide (4 + 3) Cycloaddition−Grignard Cyclization−Chugaev Elimination Sequence
2016Co-Authors: Richard P Hsung, William R Presser, Bryan J HaugenAbstract:ABSTRACT: A strategy for synthesizing highly functionalized cyclohepta[b]indoles through a concise (4 + 3) cycloaddition− cyclization−Elimination sequence is described. The cycloaddition features nitrogen-stabilized oxyallyl cations derived from epox-idations of N-aryl-N-sulfonyl-substituted allenamides, while the cyclization and Elimination employed an intramolecular Grignard addition and a one-step Chugaev process, respectively. Cyclohepta[b]indoles represent a prevalent structural motifamong pharmaceutical entities as well as bioactive natural products such as ervitsine,1 aristolasol,2 silicine,3 ambigune E,4 and actinophyllic acid (Figure 1).5 Cyclohepta[b]indole derivatives have been shown to inhibit adipocyte fatty acid binding protein (A-FABP)6 and of deacetylase SIRT1.7 Consequently, cyclohepta[b]indoles have received much attention from the synthetic community. Previous approaches8 include Fischer indole syntheses,9 ring expansions,10 an
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An Approach to Cyclohepta[b]indoles through an Allenamide (4 + 3) Cycloaddition–Grignard Cyclization–Chugaev Elimination Sequence
2015Co-Authors: Richard P Hsung, William R. Presser, Bryan J HaugenAbstract:A strategy for synthesizing highly functionalized cyclohepta[b]indoles through a concise (4 + 3) cycloaddition–cyclization–Elimination sequence is described. The cycloaddition features nitrogen-stabilized oxyallyl cations derived from epoxidations of N-aryl-N-sulfonyl-substituted allenamides, while the cyclization and Elimination employed an intramolecular Grignard addition and a one-step Chugaev process, respectively
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an approach to cyclohepta b indoles through an allenamide 4 3 cycloaddition grignard cyclization Chugaev Elimination sequence
ChemInform, 2014Co-Authors: Richard P Hsung, William R Presser, Bryan J HaugenAbstract:A strategy for synthesizing highly functionalized cyclohepta[b]indoles through a concise (4 + 3) cycloaddition–cyclization–Elimination sequence is described. The cycloaddition features nitrogen-stabilized oxyallyl cations derived from epoxidations of N-aryl-N-sulfonyl-substituted allenamides, while the cyclization and Elimination employed an intramolecular Grignard addition and a one-step Chugaev process, respectively.
Mathias Destarac - One of the best experts on this subject based on the ideXlab platform.
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Scope and Limitations of Xanthate-Mediated Synthesis of Functional γ‑Thiolactones
2018Co-Authors: Marvin Langlais, Olivier Coutelier, Mathias DestaracAbstract:A modular platform based on free-radical xanthate addition to alkenes enables access to a large series of functional γ-thiolactones. This methodology includes two different pathways based on xanthate chemistry involving radical addition and Chugaev Elimination steps. The first method uses the addition of an ester-functionalized xanthate to various commercially functional alkenes, whereas the second one is based on the addition of functional xanthates to an ester-functionalized alkene. In both cases, a series of xanthate/alkene monoadducts was obtained, and their thermolysis and subsequent cyclization led to a library of functional γ-thiolactones in moderate to good yield. For a few cases where it may not be possible to directly incorporate some targeted functional groups via the proposed process involving free radicals and high temperature, a bromo-functionalized thiolactone was used as a starting material for chemical transformations
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Straightforward Xanthate-Mediated Synthesis of Functional γ-Thiolactones and Their Application to Polymer Synthesis and Modification
Macromolecules, 2017Co-Authors: Marvin Langlais, Olivier Coutelier, Ihor Kulai, Mathias DestaracAbstract:Thiolactones allow catalyst-free polymer synthesis and modification under stoichiometric conditions at mild temperatures, without the need for tedious and costly purification steps. However, there is a need for simple and general methods for the preparation of functional thiolactones. We have developed a modular platform for γ-thiolactone synthesis based on free-radical xanthate addition to alkenes. Because of the ready availability of a great variety of functional vinyl, allyl, and maleimido derivatives, numerous substituents (exemplified here through alkyl, perfluoroalkyl, diethyl phosphonate, and N-substituted succinimidyl groups) could be efficiently attached to the γ-position of the thiolactone ring. A second substituent may be added in the α-position by proper selection of the xanthate leaving group. In all cases the target thiolactone was obtained in good yield from the xanthate:alkene monoadduct by consecutive Chugaev Elimination and cyclization. The potential of these new substituted thiolactone ...
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Straightforward Xanthate-Mediated Synthesis of Functional γ‑Thiolactones and Their Application to Polymer Synthesis and Modification
2017Co-Authors: Marvin Langlais, Olivier Coutelier, Ihor Kulai, Mathias DestaracAbstract:Thiolactones allow catalyst-free polymer synthesis and modification under stoichiometric conditions at mild temperatures, without the need for tedious and costly purification steps. However, there is a need for simple and general methods for the preparation of functional thiolactones. We have developed a modular platform for γ-thiolactone synthesis based on free-radical xanthate addition to alkenes. Because of the ready availability of a great variety of functional vinyl, allyl, and maleimido derivatives, numerous substituents (exemplified here through alkyl, perfluoroalkyl, diethyl phosphonate, and N-substituted succinimidyl groups) could be efficiently attached to the γ-position of the thiolactone ring. A second substituent may be added in the α-position by proper selection of the xanthate leaving group. In all cases the target thiolactone was obtained in good yield from the xanthate:alkene monoadduct by consecutive Chugaev Elimination and cyclization. The potential of these new substituted thiolactone building blocks for polymer chemistry was demonstrated via an amine–thiol–ene conjugation strategy which resulted in successful end-functionalization of amino-terminated polymers and a thiol–acrylate step-growth polymerization to prepare functional poly(ester amide)s. This versatile method for making functional thiolactones should find broad applications as a means to prepare new materials with original properties
Kelvin Kau Kiat Goh - One of the best experts on this subject based on the ideXlab platform.
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A Synthesis of (1E,3E)-TMS Dienes from Keto-Xanthates via Chugaev-Type Elimination
Journal of Organic Chemistry, 2013Co-Authors: Kelvin Kau Kiat Goh, Sunggak Kim, Samir ZardAbstract:An efficient route leading to exclusively (1E,3E)-TMS dienes is described. Radical xanthate addition of keto-xanthates to vinyltrimethylsilane followed by one-pot Chugaev Elimination/cyclization and in situ oxidation with m-CPBA afforded the corresponding TMS 2-sulfolenes. Isomerization to 3-sulfolenes by the action of DBU with the extrusion of sulfur dioxide in refluxing toluene gave the titled (1E,3E)-TMS dienes.