- Alkylation of Terminal Alkynes under Zinc Lewis Acid Catalysis and Its Mechanistic Studies
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With a zinc Lewis acid catalyst and proton sponge in toluene, terminal alkynes were found to undergo the alkylation by alkyl triflates to provide unsymmetrical internal alkynes. This is the first example that a simple alkyl chain other than benzylic and norbornyl units can be introduced onto the alkynyl carbon atom under Lewis acid catalysis. Mechanistic studies revealed that the activation of the alkyne by the zinc Lewis acid and proton sponge is the trigger of the reaction to give a monoalkynylzinc species, which successively reacts with the alkyl triflate to afford the internal alkyne. A radical pathway is unlikely in this system. (Figure presented.).
- Osano, Mana,Kida, Takeru,Yonekura, Kyohei,Tsuchimoto, Teruhisa
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supporting information
p. 2825 - 2831
(2019/04/13)
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- Controlled Single and Double Iodofluorination of Alkynes with DIH- and HF-Based Reagents
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A novel protocol for the regio- and stereoselective iodofluorination of internal and terminal alkynes using 1,3-diiodo-5,5,-dimethylhydantoin and HF-based reagents is disclosed. This approach is used to prepare a fluorinated tamoxifen derivative in two steps from commercially available starting materials. A facile method enabling controlled regioselective double iodofluorination of terminal alkynes is also presented.
- Pfeifer, Lukas,Gouverneur, Véronique
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supporting information
p. 1576 - 1579
(2018/03/23)
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- Expanding the scope of arylsulfonylacetylenes as alkynylating reagents and mechanistic insights in the formation of Csp2-Csp and Csp 3-Csp bonds from organolithiums
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We describe the unexpected behavior of the arylsulfonylacetylenes, which suffer an "anti-Michael" addition of organolithiums producing their alkynylation under very mild conditions. The broad scope, excellent yields, and simplicity of the experimental procedure are the main features of this methodology. A rational explanation of all these results can be achieved by theoretical calculations, which suggest that the association of the organolithiums to the electrophile is a previous step of their intramolecular attack and is responsible for the unexpected "anti-Michael" reactions observed for substituted sulfonylacetylenes. A calculated conclusion: A new transition-metal-free strategy for the synthesis of any kind of alkynyl derivatives in high yields in the reaction of organolithium species with arylsulfonylacetylenes is presented (see scheme). Theoretical calculations provide a rational explanation and suggest that association of the organolithium to the electrophile is a previous step of their intramolecular attack and is responsible for the "anti-Michael" reaction. Copyright
- Garcia Ruano, Jose Luis,Aleman, Jose,Marzo, Leyre,Alvarado, Cuauhtemoc,Tortosa, Mariola,Diaz-Tendero, Sergio,Fraile, Alberto
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supporting information; experimental part
p. 8414 - 8422
(2012/07/27)
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- Gold-catalyzed highly regioselective oxidation of C-C triple bonds without acid additives: Propargyl moieties as masked α,β-unsaturated carbonyls
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Gold-catalyzed intermolecular oxidations of internal alkynes have been achieved with high regioselectivities using 8-alkylquinoline N-oxides as oxidants and in the absence of acid additives. Synthetically versatile α,β-unsaturated carbonyls are obtained in good to excellent yields and with excellent E-selectivities. A range of functional groups such as THP, MOMO, N3, OTBS, and N-Boc are tolerated. This reaction allows α,β-unsaturated carbonyls to be masked as propargyl moieties, thus offering a practical solution to compatibility issues with these functional groups likely encountered in syntheses of complex structures.
- Lu, Biao,Li, Chaoqun,Zhang, Liming
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supporting information; experimental part
p. 14070 - 14072
(2011/01/04)
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- Transformation of β-chalcogeno alkenylboranes into tetrasubstituted olefins
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In view of generating trisubstituted vinylic chalcogen derivatives, β-chalcogeno alkenylboranes generated through the chalcogen electrophile induced rearrangements of 1-alkynyltrialkyl borates have been subjected to Suzuki-Miyaura coupling and to boron to copper transmetalation followed by alkylation. Some of the trisubstituted vinyl sulfides obtained by this latter strategy have been converted efficiently into the title olefins through the NiCl2(dmpe) catalyzed coupling with various Grignard reagents.
- Gerard, Julien,Hevesi, László
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p. 367 - 381
(2007/10/03)
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- Chalcogen electrophile induced rearrangement of 1-alkynyltrialkyl borates: Controlled syntheses of trisubstituted olefins from 1-alkynes
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The reaction of 1-alkynyltrialkyl borates with sulfenyl, selenenyl and tellurenyl halides produces β-chalcogeno alkenylboranes in good yields, with a cis relationship between the boron and the chalcogen moities. Protodeborylation of these compounds by acetic acid, or by a transmetalation-protonolysis sequence, leads to vinyl chalcogenides, which can be converted to alkenes by means of a nickel catalyzed coupling with Grignard reagents. Since the last two steps occur with retention of the stereochemistry, the overall sequence represents a highly regio- and stereoselective olefin synthesis.
- Gerard, Julien,Hevesi, László
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p. 9109 - 9121
(2007/10/03)
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- Vinylborane and vinyichalcogenide mediated syntheses of tri- and tetrasubstituted olefins from 1-alkynes
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The title olefins have been prepared with high regio- and stereocontrol from 1-alkynes through vinyl boranes 1 vinyl chalcogenides; the reaction sequences involved protonolysis or transmetallation - alkylation of the boranes followed by an Ni(0) catalyzed coupling reaction.
- Gerard, Julien,Bietlot, Emerance,Hevesi, Laszlo
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p. 8735 - 8738
(2007/10/03)
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- Substituted 4-(alka-1,2-dienylsulfinyl)morpholines: preparation and conversion into the corresponding sulfinic esters and alkynes by hydrolytic desulfinylation
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By reaction with morpholine-4-sulfenyl chloride in the presence of triethylamine, several substituted propargylic alcohols were converted into the corresponding allenic sulfinamides 3.As a complementary method, some new allenic α-lithio sulfinamides were prepared and efficiently alkylated with organic halides.The boron trifluoride/etherate-catalyzed treatment of the allenic sulfinamides with simple saturated, allylic or propargylic alcohols provided the corresponding alka-1,2-dienesulfinic esters.Oxidation of various N,N-disubstituted allenic sulfinamides yielded the allenic sulfonamides.The acid-catalyzed hydrolysis or deuterolysis of the title sulfinamides provided the corresponding alkynes.Keywords: -sigmatropic rearrangement / α-allenic sulfinamide / organolithium derivative / α-allenic sulfinic ester / retro-ene reaction / sulfur dioxide elimination / alkyne
- Baudin Jean-Bernard,Julia, Sylvestre A,Wang, Yuan
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p. 739 - 753
(2007/10/02)
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- SUBSTITUTED 4-(1',2'-ALKADIENESULPHINYL)-MORPHOLINES; PREPARATION AND HYDROLYTIC DESULPHINYLATION INTO THE CORRESPONDING ALKYNES
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By the reaction with 4-morpholinesulphenyl chloride carried out in the presence of triethylamine, several substituted propargylic alcohols have been converted into the corresponding allenic sulphinamides 2.As a complementary method, the new allenic lithio-derivatives II have been prepared and efficiently alkylated with organic halides.The acid-catalysed hydrolysis or deuterolysis of the title sulphinamides 2 provide the corresponding alkynes.
- Baudin, Jean-Bernard,Julia, Sylvestre A.,Wang, Yuan
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p. 4965 - 4968
(2007/10/02)
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- Vinylic Organoboranes. 1. A Convenient Synthesis of Acetylenes via the Reaction of Lithium (1-Alkynyl)organoborates with Iodine
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Lithium (1-alkynyl)organoborates, readily prepared from organoboranes and lithium acetylides, undergo a facile reaction at low temperature with iodine to for internal acetylenes in high yield.Unlike conventional methods for the preparation of acetylenes via nucleophilic displacement, the reaction is applicable to both primary and secondary as well as aromatic and functionally substituted groups.The use of lithium acetylide-ethylenediamine form the formation of the organoborate extends the reaction to terminal acetylenes.This reaction occurs with complete retention of the configuration about the boron-carbon bond.The procedure, with its exceptionally broad applicability, provides a simple, general route to internal and terminal acetylenes.
- Suzuki, Akira,Miyaura, Norio,Abiko, Shigeo,Itoh, Mitsuomi,Midland, M., Mark,et al.
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p. 4507 - 4511
(2007/10/02)
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- Direct Photolysis of 1-Halo-1-hexynes. Lack of Ionic Behavior
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Direct photolyses at >200 nm of 1-bromo- and 1-iodo-1-hexynes were performed in polar and nonpolar solvents.Only radical-derived products were obtained even in polar solvents, contrary to the previously reported ionic photochemical behavior of alkyl and vinyl halides.The results are discussed from an energy point of view; the ionization potential of the initially formed organic radical well accounts for the obvious difference in photobehavior between alkynyl and alkyl or vinyl halides.
- Inoue, Yoshihisa,Fukunaga, Takao,Hakushi, Tadao
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p. 1732 - 1737
(2007/10/02)
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