- Iterative synthesis of alkenes by insertion of lithiated epoxides into boronic esters
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The insertion of lithiated epoxides into boronic esters followed by thermal syn-elimination provides a stereospecific entry to alkenes. This process avoids transition metals and is amenable to iteration to provide higher substitution patterns.
- Bojaryn, Kevin,Fritsch, Stefan,Hirschhaüser, Christoph
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supporting information
p. 2218 - 2222
(2019/04/10)
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- Unexpected and powerful effect of chlorobenzene in direct palladium-catalyzed cascade Sonogashira-hydroarylation reaction
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A ubiquitous accelerating effect of chlorobenzene (PhCl) was observed unexpectedly in the Pd-catalyzed cascade Sonogashira-hydroarylation reaction. This new type of carbon-carbon bond forming cross-coupling reaction was efficiently catalysed by Pd2(dba)3 in the presence of a catalytic amount of PhCl, which provides a facile and direct approach to the synthesis of trisubstituted olefins.
- Yu, Bo,Xu, Wei,Sun, Huaming,Yu, Binxun,Zhang, Guofang,Xu, Li-Wen,Zhang, Weiqiang,Gao, Ziwei
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p. 8351 - 8354
(2015/02/19)
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- Ambient arylmagnesiation of alkynes catalysed by ligandless nickel(ii)
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A simple and efficient catalytic arylmagnesiation of diarylacetylenes and aryl(alkyl)acetylenes is accomplished by NiCl2·6H2O at r.t. in the absence of stabilising ligands. The corresponding tetra-substituted alkenes can be obtained in good yields by subsequent treatment with different electrophiles. The Royal Society of Chemistry 2013.
- Xue, Fei,Zhao, Jin,Hor, T. S. Andy
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p. 10121 - 10123
(2013/10/22)
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- Novel alkylidenating agents of iron(III) derivatives by base-mediated α,μ-dehydrohalogenation and their chemical trapping by cycloaddition
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Studies of the reactions between group 4 metal, chlorides (M = Ti, Zr, Hf) and methyllithium at -78 °C in toluene can lead to methylidene-metal complexes, H2C=MCl2, by a sequence of monomethylation, α-carbon lithiation and α,μ-elimination of LiCl. Here study of the preparation of alkylidene derivatives of iron was attempted by the interaction of FeCl3 with n-butyllithium in various ratios at -78 °C. The presence of any resulting butylidene-iron(III) derivative, nPrCH=FeE (E = Cl, nBu), was probed by adding chemical trapping agents, such as diphenylacetylene, benzonitrile, methyl benzoate and benzophenone. In each experiment the hydrolyzed products were consistent with a cycloaddition reaction of nPrCH=FeE with the trapping agent. The products from, di-phenylacetylene and from, benzonitrile with D2O workup are uniquely in accord with such a carbene precursor. A 3:1 ratio of nBuLi/FeCl3 gave the optimal yield of nPrCH=FenBu, ca. 80%, from, the MBu2FeCl precursor. When a 3:1. reaction mixture was simply brought to 25 °C and hydrolyzed, the purple alkylidene-iron complex decomposed completely to iron metal. A study of a 3:1 interaction of PhCH2MgCl and FeCl3 under similar conditions and trapping with diphenylacetylene provided evidence for the formation of PhCH=FeCH2Ph in ca. 40%. These results support; the hope that alkylidene-iron(III) analogs of the Grubbs reagents may be accessible by this process.
- Eisch, John J.,Sohn, Jane U.,Rabinowitz, Edon J.
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experimental part
p. 2971 - 2977
(2010/08/20)
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- Palladium-catalyzed hydrophenylation of alkynes with sodium tetraphenylborate under mild conditions
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(Chemical Equation Presented) In an aqueous solution of acetic acid, PdCl2(PPh3)2 showed high catalytic activity for the hydrophenylation of both terminal and internal alkynes with sodium tetraphenylborate (NaBPh4) under mild conditions, affording phenyl alkenes in moderate to excellent yields.
- Zeng, Hanxiang,Hua, Ruimao
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p. 558 - 562
(2008/09/17)
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- Silylzincation of carbon-carbon multiple bonds revisited
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The first investigation of the copper-catalyzed silylzincation of alkynes as well as a diene and styrene using bis(triorganosilyl) zinc reagents led to the development of an efficient procedure and the disclosure of an unexpected bissilylation and unfores
- Auer, Gertrud,Oestreich, Martin
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p. 311 - 313
(2008/02/08)
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- Carbolithiation of diphenylacetylene as a stereoselective route to (Z)-tamoxifen and related tetrasubstituted olefins
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(Chemical Equation Presented) Carbolithiation of diphenylacetylene can be exploited to generate (E)-1-lithio-1,2-diphenylalkyl-1-enes which can be reacted in situ with triisopropylborate to stereoselectively provide (E)-1,2-diphenyl-1-alkylene boronic acids. These tetrasubstituted vinylboronic acids served as versatile intermediates for the generation of tetrasubstituted olefins with retention of stereochemistry. The application of this method for the stereoselective synthesis of (Z)-tamoxifen and related analogues is described.
- McKinley, Neola F.,O'Shea, Donal F.
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p. 9552 - 9555
(2007/10/03)
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- The Peterson olefination using the tert-butyldiphenylsilyl group: Stereoselective synthesis of di- and trisubstituted alkenes
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The reaction of α-tert-butyldiphenylsilyl carbonyl compounds with organometallics leads with a high diastereoselectivity to erythro-β-hydroxysilanes, which under acidic or basic elimination conditions give E or Z di- and trisubstituted alkenes.
- Barbero,Blanco,Garcia,Pulido
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p. 1223 - 1228
(2007/10/03)
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- DIRECT PREPARATION OF SUBSTITUTED OLEFINS FROM EPOXIDES UTILIZING LITHIUM TETRAALKYLCERATE
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Alkylated olefins were directly synthesized in good yields by the deoxygenation reaction of epoxides with concomitant introduction of the alkyl group using lithium tetraalkylcerate.Styreneoxide and (1-naphtyl)ethyleneoxide gave terminal olefins, while ethyleneoxide replaced by alphatic substituent, 1,2-epoxy-4-phenylbutane, afforded internal olefin.The utility of the present method was demonstrated in the one-step synthesis of a sesquiterpene, dehydro-α-curcumene.
- Ukaji, Yutaka,Fujisawa, Tamotsu
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p. 5165 - 5168
(2007/10/02)
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