- A copper (I or II)/diethylphosphite catalytic system for base-free additive dimerization of alkynes
-
Copper (I) or copper (II) salts and oxides promote regioselective head-to-head additive dimerization of aromatic and aliphatic terminal alkynes in the presence a catalytic amount of diethylphosphite. The reaction proceeds under ambient conditions without
- Trostyanskaya, Inna G.,Beletskaya, Irina P.
-
supporting information
p. 148 - 153
(2016/12/23)
-
- A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes
-
Frustrated Lewis pairs are compounds containing both Lewis acidic and Lewis basic moieties, where the formation of an adduct is prevented by steric hindrance. They are therefore highly reactive, and have been shown to be capable of heterolysis of molecular hydrogen, a property that has led to their use in hydrogenation reactions of polarized multiple bonds. Here, we describe a general approach to the hydrogenation of alkynes to cis-alkenes under mild conditions using the unique ansa-aminohydroborane as a catalyst. Our approach combines several reactions as the elementary steps of the catalytic cycle: hydroboration (substrate binding), heterolytic hydrogen splitting (typical frustrated-Lewis-pair reactivity) and facile intramolecular protodeborylation (product release). The mechanism is verified by experimental and computational studies.
- Chernichenko, Konstantin,Madarasz, Adam,Papai, Imre,Nieger, Martin,Leskelae, Markku,Repo, Timo
-
p. 718 - 723
(2013/08/23)
-
- Gold-catalyzed cyclizations of cis-enediynes: Insights into the nature of gold-aryne interactions
-
Golden aryne? Gold aryne complexes are inferred as transition states in dual gold-catalyzed cyclizations of cis-enediynes (see scheme; DCE=1,2-dichloroethane). They are better described as ortho-aurophenyl cations, which react with weak nucleophiles and undergo facile intramolecular insertions into C(sp3)-H bonds. Indanes, fused heteroarenes, and phenol derivatives are readily prepared using this method. Copyright
- Wang, Youliang,Yepremyan, Akop,Ghorai, Subir,Todd, Robert,Aue, Donald H.,Zhang, Liming
-
supporting information
p. 7795 - 7799
(2013/08/23)
-
- Silaborations of 1,3-enynes - Substrate controlled allene/1,3-diene selectivity
-
(Chemical Equation Presented) Silaboration of 1,3-enynes catalyzed by group 10 metal complexes affords 1,3-dienes with vinylborane and vinylsilane functions or 1,2-dienes with allylborane and vinylsilane functions. The type of product formed is determined
- Lueken, Christian,Moberg, Christina
-
supporting information; experimental part
p. 2505 - 2508
(2009/05/26)
-
- Dialkyltitanium-mediated titanation of conjugated 1,3-butadiynes and its coupling reactions with aldehydes: a facile synthesis of stereodefined enynes and trans-enynols
-
A highly efficient and convenient method for the selective titanation of 1,3-butadiynes using Ti(OiPr)4/nBuLi reagent has been developed. The method provided a facile synthesis of enynes and trans-enynols in a well-stereod
- Chen, Jingjin,Liu, Yuanhong
-
supporting information; experimental part
p. 6655 - 6658
(2009/04/07)
-
- Oligomerization and hydroamination of terminal alkynes promoted by the cationic organoactinide compound [(Et2N)3U][BPh4]
-
The three ancillary amido moieties in the cationic complex [(Et2N)3U][BPh4] are highly reactive and are easily replaced when the complex is treated with primary amines. The reaction of [(Et2N)3U][BPh4] with excess tBuNH2 allows the formation of the cationic complex [(tBuNH2)3(tBu-NH)3U][BPh4]. X-ray diffraction studies on the complex indicate that three amido and three amine ligands are arranged around the cationic metal center in a slightly distorted octahedral mer geometry. The cationic complex reacts with primary alkynes in the presence of external primary amines to primarily afford the unexpected cis dimer and, in some cases, the hydroamination products are obtained concomitantly. The formation of the cis dimer is the result of an envelope isomerization through a metal - cyclopropyl cationic complex. In the reaction of the bulkier alkyne tBuC≡CH with the cationic uranium complex in the presence of various primary amines, the cis dimer, one trimer, and one tetramer are obtained regioselectively, as confirmed by deuterium labeling experiments. The trimer and the tetramer correspond to consecutive insertions of an alkyne molecule into the vinylic CH bond trans to the bulky tert-butyl group. The reaction of (TMS)C≡CH with the uranium catalyst in the presence of EtNH2 followed a different course and produced the gem dimer along with the hydroamination imine as the major product. However, when other bulkier amines were used (iPrNH2 or tBuNH2) both hydroamination isomeric imines Z and E were obtained. During the catalytic reaction, the E (kinetic) isomer is transformed into the most stable Z (thermodynamic) isomer. The unique reactivity of the alkyne (TMS)C≡CH with the secondary amine Et2NH is remarkable because it afforded the trans dimer and the corresponding hydroamination enamine. The latter probably results from the insertion of the alkyne into a secondary metalamide bond, followed by protonolysis.
- Wang, Jiaxi,Dash, Aswini Kumar,Kapon, Moshe,Berthet, Jean-Claude,Ephritikhine, Michel,Eisen, Moris S.
-
p. 5384 - 5396
(2007/10/03)
-
- Regio- and stereoselective dimerization of terminal alkynes to enynes catalyzed by a palladium/imidazolium system
-
A Palladium/imidazolium chloride system has been used to mediate the dimerization of terminal alkynes to enynes. The combination of 1 mol % Pd(OAc)2 and 2 mol % IMes·HCl in the presence of Cs2CO3 as base shows high activit
- Yang, Chuluo,Nolan, Steven P.
-
p. 591 - 593
(2007/10/03)
-
- Ruthenium catalyzed homocoupling of terminal alkynes
-
Several complexes of the type RuTp(L)(L′)Cl (L, L′ = P, N, O donors) were tested with respect to their ability of promoting catalytic C-C-coupling reactions of terminal acetylenes. When L = tertiary phosphine, predominantly dimerization occurs, RuTp(PPhs
- Slugovc, Christian,Doberer, Daniel,Gemel, Christian,Schmid, Roland,Kirchner, Karl,Winkler, Berthold,Stelzer, Franz
-
p. 221 - 233
(2007/10/03)
-
- Head-to-head Z Dimerization of Terminal Alkynes Catalyzed by Thiolate-bridged Diruthenium Complexes
-
The thiolate-bridged diruthenium complexes (R=Me, Et, nPr) were found to be effective and highly selective catalysts for the head-to-head Z dimerization of various terminal alkynes including straight-chain aliphatic alky
- Que, Jing-Ping,Masui, Dai,Ishii, Youichi,Hidai, Masanobu
-
p. 1003 - 1004
(2007/10/03)
-
- Stereochemistry of direct olefin formation from carbonyl compounds and lithiated heterocyclic sulfones
-
The conditions for the title reaction were studied for the 2-benzothiazole and 2-pyridine series and for some examples in the 2-pyrimidine series.The olefin preparations were generally observed to be more efficient for 2-BT-sulfone systems.From the data of the hundred cases studied, it can be concluded that (E)-olefins are obtained: (i) from saturated BT-sulfones and aromatic aldehydes; and (ii) from benzylic BT-sulfones and branched saturated aldehydes (isobutyraldehyde, pivalaldehyde) or α,β-ethylenic or aromatic aldehydes. (Z)-olefins arise: (i) fom propargylic BT-sulfones and saturated or aromatic aldehydes; and (ii) from allylic or benzylic Pyr-sulfones and saturated aldehydes.Possible mechanisms for this new olefination procedure were examined. - heteroaromatic sulfones, organolithium derivatives, intramolecular ipso reactions, stereochemistry, elimination, olefination.
- Baudin, J. B.,Hareau, G.,Julia, S. A.,Lorne, R.,Ruel, O.
-
p. 856 - 878
(2007/10/02)
-
- Oligophosphan-Liganden XXXII. Katalytische Dimerisierung von 1-Alkinen zu linearen 1-En-3-inen an cis-Arylhydridoruthenium(II)Chelatkomplexen. Molekuelstruktur von (pp3)RuH(C6H4CF3-3) (pp3 = P(CH2CH2CH2PMe2)3)
-
The complexes L4RuH(C6H5) with L4 = P(CH2CH2CH2PMe2)3, N(CH2CH2PPh2)3, and MeSi(CH2PMe2)3/PMe3 all serve as catalysts for the dimerization of 1-alkynes, RCCH (R = C6H5, n-C4H9, t-C4H9).The reaction proceeds to yield 1,4-disubstituted 1-en-3-ynes.RCH=CH
- Dahlenburg, L.,Frosin, K.-M.,Kerstan, S.,Werner, D.
-
p. 115 - 124
(2007/10/02)
-
- Carbon-Carbon Bond Formation via Opening of Epoxysilanes with Organometals Containing Lithium and Copper
-
Various types of organometals containing lithium and copper react with E and Z epoxysilanes to produce adducts which, either under the reaction conditions or upon treatment with a base, e.g., KH, can be stereospecifically converted to the corresponding E and Z alkenes, respectively.
- Zhang, Yantao,Miller, Joseph A.,Negishi, Ei-ichi
-
p. 2043 - 2044
(2007/10/02)
-
- Configurational Instability of α-Alkenyl and α-Alkynyl Vinyllithiums. Syntheses of Stereodefined 2-Alkyl-1-en-3-ynes
-
Metal-halogen exchange of either (Z)-enynyl bromides or (Z)-dienyl bromides by sec-BuLi produces vinyllithiums that are configurationally stable only at temperatures below -120 deg C and -78 deg C, respectively.Allylation of (Z)-enynylalanates with allyl bromide or methylation of (Z)-enynyl bromides with CH3MgI and Fe(acac)3 catalyst furnishes the corresponding 2-alkyl-1-en-3-ynes.
- Miller, Joseph A.,Leong, William,Zweifel, George
-
p. 1839 - 1840
(2007/10/02)
-