- A new cine-substitution of alkenyl sulfones with aryltitanium reagents catalyzed by rhodium: Mechanistic studies and catalytic asymmetric synthesis of allylarenes
-
The reaction of alkenyl sulfones with aryltitanium triisopropoxide (ArTi(OPr-i )3) in the presence of 3 mol % of [Rh(OH)((S)-binap)]2 in THF at 40 °C gave high yield of cine-substitution products. The catalytic cycle was established by deuterium-labeling studies, and it was applied to catalytic asymmetric synthesis of allylarenes which proceeds with over 99% enantioselectivity. Copyright
- Yoshida, Kazuhiro,Hayashi, Tamio
-
-
Read Online
- Dinuclear cobalt complex-catalyzed stereodivergent semireduction of alkynes: Switchable selectivities controlled by H2O
-
Catalytic semireduction of internal alkynes to alkenes is very important for organic synthesis. Although great success has been achieved in this area, switchable Z/E stereoselectivity based on a single catalyst for the semireduction of internal alkynes is a longstanding challenge due to the multichemo- and stereoselectivity, especially based on less-expensive earth-abundant metals. Herein, we describe a switchable semireduction of alkynes to (Z)- or (E)-alkenes catalyzed by a dinuclear cobalt complex supported by a macrocyclic bis pyridyl diimine (PDI) ligand. It was found that cis-reduction of the alkyne occurs first and the Z-E alkene stereoisomerization process is formally controlled by the amount of H2O, since the concentration of H2O may influence the catalytic activity of the catalyst for isomerization. Therefore, this protocol provides a facile way to switch to either the (Z)- or (E)-olefin isomer in a single transformation by adjusting the amount of water.
- Chen, Ke,Zhu, Hongdan,Li, Yuling,Peng, Qian,Guo, Yinlong,Wang, Xiaoming
-
p. 13696 - 13705
(2021/11/16)
-
- Dilithium Amides as a Modular Bis-Anionic Ligand Platform for Iron-Catalyzed Cross-Coupling
-
Dilithium amides have been developed as a bespoke and general ligand for iron-catalyzed Kumada-Tamao-Corriu cross-coupling reactions, their design taking inspiration from previous mechanistic and structural studies. They allow for the cross-coupling of alkyl Grignard reagents with sp2-hybridized electrophiles as well as aryl Grignard reagents with sp3-hybridized electrophiles. This represents a rare example of a single iron-catalyzed system effective across diverse coupling reactions without significant modification of the catalytic protocol, as well as remaining operationally simple.
- Neate, Peter G.N.,Zhang, Bufan,Conforti, Jessica,Brennessel, William W.,Neidig, Michael L.
-
supporting information
p. 5958 - 5963
(2021/08/18)
-
- Ruthenium-Catalyzed E-Selective Partial Hydrogenation of Alkynes under Transfer-Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source
-
E-alkenes were synthesized with up to 100 % E/Z selectivity via ruthenium-catalyzed partial hydrogenation of different aliphatic and aromatic alkynes under transfer-hydrogenation conditions. Paraformaldehyde as a safe, cheap and easily available solid hydrogen carrier was used for the first time as hydrogen source in the presence of water for transfer-hydrogenation of alkynes. Optimization reactions showed the best results for the commercially available binuclear [Ru(p-cymene)Cl2]2 complex as pre-catalyst in combination with 2,2-bis(diphenylphosphino)-1,1-binaphthyl (BINAP) as ligand (1 : 1 ratio per Ru monomer to ligand). Mechanistic investigations showed that the origin of E-selectivity in this reaction is the fast Z to E isomerization of the formed alkenes. Mild reaction conditions plus the use of cheap, easily available and safe materials as well as simple setup and inexpensive catalyst turn this protocol into a feasible and promising stereo complementary procedure to the well-known Z-selective Lindlar reduction in late-stage syntheses. This procedure can also be used for the production of deuterated alkenes simply using d2-paraformaldehyde and D2O mixtures.
- Fetzer, Marcus N. A.,Tavakoli, Ghazal,Klein, Axel,Prechtl, Martin H. G.
-
p. 1317 - 1325
(2021/02/11)
-
- Precatalyst-Enabled Selectivity: Enantioselective NiH-Catalyzed anti-Hydrometalative Cyclization of Alkynones to Endo- and Heterocyclic Allylic Alcohols
-
A highly enantioselective NiH-catalyzed hydrocyclization of alkynones with unparalleled anti- and endocyclic selectivities is described. The choice of the precatalysts has significant influence in tuning the regio- and enantioselectivity. Using Ni(OTs)su
- Li, Qi-Yang,Liu, Wen-Bo,Zeng, Hai-Xiang,Zhang, Xiao-Wen,Zhu, Ming-Hui
-
supporting information
p. 27225 - 27229
(2021/12/08)
-
- Covalent Organic Framework as a Heterogeneous Ligand for the Regioselective Oxidative Heck Reaction
-
A simple imine-based covalent organic framework (COF) as heterogeneous ligand for PdII-promoted Heck reaction is reported. Good regioselectivity for a wide range of electronically unbiased olefins is obtained (linear/branched >100:1 in most cases). Related tests and density functional theory calculations are used to explore the reason underlying the high selectivity. This research opens a route for COF as an intriguing platform to control regioselectivity catalysis.
- Han, Jiyao,Sun, Xiaowei,Wang, Xiao,Wang, Qiong,Hou, Shenghuai,Song, Xin,Wei, Yingqin,Wang, Rongyu,Ji, Wenhua
-
supporting information
p. 1480 - 1484
(2020/03/13)
-
- ISOMERIZATION OF ALKENES
-
The present invention relates to an isomerization method for alkenes, comprising of reaction an alkene with a Ni(I)-compound. By this method, E-Alkenes are obtained in excellent yield.
- -
-
Page/Page column 20-21; 25; 26
(2020/04/25)
-
- Designing a Planar Chiral Rhodium Indenyl Catalyst for Regio- And Enantioselective Allylic C-H Amidation
-
Chiral variants of group IX Cp and Cp? catalysts are well established and catalyze a broad range of reactions with high levels of enantioselectivity. Enantiocontrol in these systems results from ligand design that focuses on appropriate steric blocking. Herein we report the development of a new planar chiral indenyl rhodium complex for enantioselective C-H functionalization catalysis. The ligand design is based on establishing electronic asymmetry in the catalyst, to control enantioselectivity during the reactions. The complex is easily synthesized from commercially available starting materials and is capable of catalyzing the asymmetric allylic C-H amidation of unactivated olefins, delivering a wide range of high-value enantioenriched allylic amide products in good yields with excellent regio- and enantioselectivity. Computational studies suggest that C-H cleavage is rate- and enantio-determining, while reductive C-N coupling from the RhV-nitrenoid intermediate is regio-determining.
- Farr, Caitlin M. B.,Kazerouni, Amaan M.,Park, Bohyun,Poff, Christopher D.,Won, Joonghee,Sharp, Kimberly R.,Baik, Mu-Hyun,Blakey, Simon B.
-
supporting information
p. 13996 - 14004
(2020/09/18)
-
- A Bidentate Ru(II)-NC Complex as a Catalyst for Semihydrogenation of Alkynes to (E)-Alkenes with Ethanol
-
Four Ru(II)-NC complexes were tested as catalysts for semihydrogenation of internal alkynes to (E)-alkenes with ethanol, and the complex {(C5H4N)(C6H4)}RuCl(CO)(PPh3)2 (1a) showed the highest activity. The reactions proceeded well with 1 mol % catalyst loading and 0.1 equiv of t-BuONa at 110 °C for 1 h, and 32 alkenes were synthesized with excellent E:Z selectivity. This is the first ruthenium-catalyzed semihydrogenation of internal alkynes to (E)-alkenes using ethanol as the hydrogen donor.
- Chen, Dafa,Gong, Dawei,Hu, Bowen,Kong, Degong,Xia, Haiping,Yang, Weiwei
-
-
- Constructing Mononuclear Palladium Catalysts by Precoordination/Solvothermal Polymerization: Recyclable Catalyst for Regioselective Oxidative Heck Reactions
-
Heterogeneous, metal, single-site catalysts often exhibit higher catalytic performance than other catalysts because of their maximized atom efficiency of 100 %. Reported herein is a precoordination/solvothermal polymerization strategy to fabricate a stabl
- Li, Wen-Hao,Li, Cun-Yao,Xiong, Huan-Yan,Liu, Yang,Huang, Wen-Yong,Ji, Guang-Jun,Jiang, Zheng,Tang, Hai-Tao,Pan, Ying-Ming,Ding, Yun-Jie
-
supporting information
p. 2448 - 2453
(2019/02/03)
-
- Stereospecific Iron-Catalyzed Carbon(sp2)-Carbon(sp3) Cross-Coupling with Alkyllithium and Alkenyl Iodides
-
An efficient synthetic protocol involving iron-catalyzed cross-coupling reactions between organolithium compounds and alkenyl iodides as key coupling partners was achieved. More than 30 examples were obtained with moderate to good yields and high stereospecificity. Gram-scale and synthetic applications of this procedure are recorded herein to demonstrate its feasibility and potential utilization.
- Lu, Xiao-Lin,Shannon, Mark,Peng, Xiao-Shui,Wong, Henry N. C.
-
supporting information
p. 2546 - 2549
(2019/03/26)
-
- Palladium-catalyzed double-bond migration of unsaturated hydrocarbons accelerated by tantalum chloride
-
The operationally simple palladium-catalyzed double-bond migration without heteroatom-containing coordinating functional groups is described. Addition of TaCl5 as a second catalyst greatly enhanced the migration efficiency to provide β-alkylsty
- Murai, Masahito,Nishimura, Kengo,Takai, Kazuhiko
-
p. 2769 - 2772
(2019/03/23)
-
- E-Olefins through intramolecular radical relocation
-
Full control over the selectivity of carbon-carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach.We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.
- Kapat, Ajoy,Sperger, Theresa,Guven, Sinem,Schoenebeck, Franziska
-
p. 391 - 396
(2019/02/03)
-
- A Highly Reduced Ni-Li-Olefin Complex for Catalytic Kumada-Corriu Cross-Couplings
-
The catalytic activity of a highly reduced Ni catalyst in the context of a Kumada-Corriu cross-coupling has been studied. This nickel complex is characterized by its high electron density, stabilized by simple olefin ligands in combination with two Li ions. Landmark reactivity has been found with this precatalyst which operates at cryogenic temperatures, thus allowing the presence of sensitive functionalities. Structural elucidation of oxidative addition intermediates and their reactivity suggest highly reduced species being operative in the C-C bond forming event.
- Nattmann, Lukas,Lutz, Sigrid,Ortsack, Pascal,Goddard, Richard,Cornella, Josep
-
supporting information
p. 13628 - 13633
(2018/10/24)
-
- Metal-Catalyzed Remote Functionalization of ω-Ene Unsaturated Ethers: Towards Functionalized Vinyl Species
-
The combined ruthenium-catalyzed chain walking with the nickel-catalyzed cross-coupling reaction of ω-alkenyl ethers provide a unique entry to functionalized vinyl species. This transformation illustrates the power and flexibility of remote functionalization by demonstrating the compatibility of two independent reactions involving unrelated sites.
- Ho, Guo-Ming,Judkele, Lina,Bruffaerts, Jeffrey,Marek, Ilan
-
p. 8012 - 8016
(2018/06/29)
-
- Thiophene-Alkyne-Based CMPs as Highly Selective Regulators for Oxidative Heck Reaction
-
Thiophenes containing an adjacent C≡C group as ligands for PdII-promoted organic reactions are reported for the first time. These ligands were utilized as catalytic sites and integrated into the skeleton of conjugated microporous polymers. By e
- Li, Ren-Hao,Ding, Zong-Cang,Li, Cun-Yao,Chen, Jun-Jia,Zhou, Yun-Bing,An, Xiao-Ming,Ding, Yun-Jie,Zhan, Zhuang-Ping
-
p. 4432 - 4435
(2017/09/11)
-
- Conjugated Microporous Polymer as Heterogeneous Ligand for Highly Selective Oxidative Heck Reaction
-
A series of pyridine-type ligands containing C C bonds were designed and synthesized for selective oxidative Heck reaction. These ligands were utilized as functional units and integrated into the skeleton of conjugated microporous polymers. 6,6′-diiodo-2,2′-bipyridine and 1,3,5-triethynylbenzene were polycondensed via Sonogashira cross-coupling strategy to afford CMP-1 material. The resultant CMP-1 was used as a heterogeneous catalytic ligand for the PdII-catalyzed oxidative Heck reaction with high linear selectivity. The linear selectivity of CMP-1 is about 30 times higher than that of bipyridine-based monomer ligand. This work opens a new front of using CMP as an intriguing platform for developing highly efficient catalysts in controlling the regioselectivity in organic reactions.
- Zhou, Yun-Bing,Wang, Yu-Qing,Ning, Li-Chao,Ding, Zong-Cang,Wang, Wen-Long,Ding, Cheng-Ke,Li, Ren-Hao,Chen, Jun-Jia,Lu, Xin,Ding, Yun-Jie,Zhan, Zhuang-Ping
-
supporting information
p. 3966 - 3969
(2017/03/27)
-
- Palladium Stabilized by Amino-Vinyl Silica Functionalized Magnetic Carbon Nanotube: Application in Suzuki–Miyaura and Heck–Mizoroki Coupling Reactions
-
Abstract: This study describes an investigation on Suzuki and Heck cross-couplings of aryl electrophiles in the presence of heterogeneous Pd nanoparticles supported on amino-vinyl silica functionalized magnetic carbon nanotube. The core–shell contains CNT@Fe3O4@SiO2-Pd in which the functionalized SiO2 helps the stabilization of Pd nanoparticles and also responsible for the reduction of Pd(II) to Pd(0) without the need for adding external reducing agents. All of the reactions were done under phosphine-free condition. Graphical Abstract: [Figure not available: see fulltext.]
- Khalili, Dariush,Banazadeh, Ali Reza,Etemadi-Davan, Elham
-
p. 2674 - 2687
(2017/09/06)
-
- Oxygenation of Simple Olefins through Selective Allylic C?C Bond Cleavage: A Direct Approach to Cinnamyl Aldehydes
-
A novel metal-free allylic C?C σ-bond cleavage of simple olefins to give valuable cinnamyl aldehydes is reported. 1,2-Aryl or alkyl migration through allylic C?C bond cleavage occurs in this transformation, which is assisted by an alkyl azide reagent. This method enables O-atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The reaction features simple hydrocarbon substrates, metal-free conditions, and high regio- and stereoselectivity.
- Liu, Jianzhong,Wen, Xiaojin,Qin, Chong,Li, Xinyao,Luo, Xiao,Sun, Ao,Zhu, Bencong,Song, Song,Jiao, Ning
-
supporting information
p. 11940 - 11944
(2017/09/20)
-
- Olefination of N-Sulfinylimines under Mild Conditions
-
A very simple and efficient diastereoselective synthesis of 1,2-disubstituted alkenes has been achieved under mild conditions. Sulfoxide stabilised N-sulfinylimines reacted with in-situ-generated phosphonate carbanions to give 1,2-disubtituted alkenes in good to excellent yields. Different aryl phosphonates reacted with a range of electronically diverse N-sulfinylimines to give alkenes with >99:1 E selectivity. The most important feature of this protocol is that the reaction can be carried out at room temperature with inexpensive sodium hydride as the most effective base to generate the reactive phosphonate carbanions, and producing the alkenes with E selectivity in up to 85 % isolated yield.
- Dhara, Shubhendu,Diesendruck, Charles E.
-
p. 1184 - 1190
(2017/03/11)
-
- Silica-coated nano-Fe3O4-supported iminopyridine palladium complex as an active, phosphine-free and magnetically separable catalyst for Heck reactions
-
A novel magnetic nanoparticle-supported iminopyridine palladium complex was successfully prepared by attaching palladium acetate to iminopyridine ligand-functionalized silica-coated nano-Fe3O4. The as-prepared catalyst was well characterized and was evaluated in Heck reactions in terms of activity and recyclability. It was found to be highly efficient for the reactions of various aryl iodides and aryl bromides having electron-withdrawing groups with olefins under phosphine-free and inert atmosphere-free conditions. Moreover, the catalyst could be conveniently recovered using an external magnet, and the recyclability was influenced by the base in the Heck reaction. The catalyst could be reused at least six times with no significant loss in activity when triethylamine acted as the base.
- Zhang, Qiang,Zhao, Xin,Wei, Huai-Xin,Li, Ji-Hang,Luo, Jun
-
-
- Iron-Catalyzed Cross-Coupling of Alkenyl Acetates
-
Stable C-O linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong C-O bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 C, 2 h) with a ligand-free catalyst (1-2 mol%). Iron clad: Acetates are underutilized electrophiles in metal-catalyzed cross-coupling reactions because of the strong alkenyl C-O bond and their propensity to engage in unwanted reactions. Combination of a ligand-free low-valent Fe catalyst with nucleophilic organomagnesium reagents, low temperature, and short reaction times results in highly selective cross-couplings with alkenyl acetates.
- G?rtner, Dominik,Stein, André Luiz,Grupe, Sabine,Arp, Johannes,Von Wangelin, Axel Jacobi
-
supporting information
p. 10545 - 10549
(2015/09/02)
-
- Peroxide promoted tunable decarboxylative alkylation of cinnamic acids to form alkenes or ketones under metal-free conditions
-
A tunable decarboxylative alkylation of cinnamic acids with alkanes was developed to form alkenes or ketones under transition metal-free conditions. In the presence of DTBP or DTBP/TBHP, the reaction gave alkenes and ketones respectively via a radical mechanism in moderate to good yields. This journal is
- Ji, Jing,Liu, Ping,Sun, Peipei
-
supporting information
p. 7546 - 7549
(2015/05/04)
-
- Catalytic, oxidant-free, direct olefination of alcohols using Wittig reagents
-
Reported here is the catalytic, acceptorless coupling of alcohols with in situ generated, non-stabilized phosphonium ylides to form olefins as major products. The reaction uses low catalyst loadings and does not require added oxidants. Hydrogenation of the product is minimized and the reaction leads to Z (aliphatic) or E (benzylic) stereospecificity.
- Khaskin,Milstein
-
supporting information
p. 9002 - 9005
(2015/05/27)
-
- Copper catalyzed direct alkenylation of simple alkanes with styrenes
-
A novel Cu-catalyzed direct alkenylation of simple alkanes with styrenes was described. In the presence of a catalytic amount of Cu(OTf)2, a diverse range of alkenes undergo coupling with cycloalkanes to produce (E)-alkyl alkenes. This transformation is proposed to proceed via a radical process. This journal is the Partner Organisations 2014.
- Zhu, Yefeng,Wei, Yunyang
-
p. 2379 - 2382
(2014/05/20)
-
- Improved procedure for single-electron-transfer-induced grignard cross-coupling reaction
-
Aryl Grignard reagents were found to undergo coupling with aryl or alkenyl bromides in the presence of LiCl in a mixed solvent consisting of toluene and THF (2/1). Previously employed removal of THF with evacuation from Grignard solutions is no longer needed to obtain biaryls and styrene derivatives.
- Shirakawa, Eiji,Okura, Keisho,Uchiyama, Nanase,Murakami, Takuya,Hayashi, Tamio
-
supporting information
p. 922 - 924
(2014/06/23)
-
- Single-electron-transfer-induced coupling of arylzinc reagents with aryl and alkenyl halides
-
Arylzinc reagents, prepared from aryl halides/zinc powder or aryl Grignard reagents/zinc chloride, were found to undergo coupling with aryl and alkenyl halides without the aid of transition-metal catalysis to give biaryls and styrene derivatives, respectively. In this context, we have already reported the corresponding reaction using aryl Grignard reagents instead of arylzinc reagents. Compared with the Grignard cross-coupling, the present reaction features high functional-group tolerance, whereby electrophilic groups such as alkoxycarbonyl and cyano groups are compatible as substituents on both the arylzinc reagents and the aryl halides. Aryl halides receive a single electron and thereby become activated as the corresponding anion radicals, which react with arylzinc reagents, thus leading to the cross-coupling products. Arylzinc reagents were found to undergo coupling with aryl and alkenyl halides to give biaryl and styrene derivatives, respectively. The cross-coupling, which features high functional-group tolerance, proceeds through a single-electron-transfer mechanism and thus does not require the aid of transition-metal catalysis.
- Shirakawa, Eiji,Tamakuni, Fumiko,Kusano, Eugene,Uchiyama, Nanase,Konagaya, Wataru,Watabe, Ryo,Hayashi, Tamio
-
p. 521 - 525
(2014/01/23)
-
- Microwave-assisted palladium-catalyzed arylation of styrenes and alkenes with diaryliodonium salts
-
Highly effective microwave-assisted palladium-catalyzed arylation of styrenes and alkenes with diaryliodonium salts have been developed, giving styrenes in high yields without ligand in 60 s.
- Li, Jian,Liu, Li,Ding, Dong,Sun, Jiang-Tao
-
-
- Single electron transfer-induced cross-coupling reaction of alkenyl halides with aryl Grignard reagents
-
Alkenyl halides were found to undergo coupling with aryl Grignard reagents to give the corresponding styrene derivatives in a stereo-retained manner. The cross-coupling reaction is considered to proceed through a single electron transfer mechanism.
- Shirakawa, Eiji,Watabe, Ryo,Murakami, Takuya,Hayashi, Tamio
-
supporting information
p. 5219 - 5221
(2013/06/27)
-
- ZrCl2(η-C5Me5)2-AlHCl 2·(THF)2: Efficient hydroalumination of terminal alkynes and cross-coupling of the derived alanes
-
Stabilized AlHCl2·(THF)2 hydroaluminates RCCH with exceptional chemo-, regio- and stereoselectivity under efficient ZrCl 2(η-C5Me5)2 catalysis (2-5 mol%). The resulting vinyl alanes undergo palladium cross-coupling with a wide range of sp2 electrophiles (aryl, heteroaryl and vinyl halides/pseudohalides) in good to excellent yields. The Royal Society of Chemistry 2013.
- Andrews, Philip,Latham, Christopher M.,Magre, Marc,Willcox, Darren,Woodward, Simon
-
supporting information
p. 1488 - 1490
(2013/03/14)
-
- Ligand effects on the stereochemical outcome of suzuki-miyaura couplings
-
The ligands associated with various Pd catalysts play a crucial role in determining the stereochemistry of cross-couplings between boronic acids and Z-alkenyl halides. A ligand on palladium has been found that leads to the desired products under mild conditions and in high yields that, in most cases, retain their Z-olefin geometry.
- Lu, Guo-Ping,Voigtritter, Karl R.,Cai, Chun,Lipshutz, Bruce H.
-
experimental part
p. 3700 - 3703
(2012/06/15)
-
- Non-cross-linked polystyrene-supported triphenylarsonium halides and their use in the arsa-Wittig reaction
-
Non-cross-linked polystyrene-supported (carbomethoxymethyl) triphenylarsonium bromide (1) and benzyltriphenylarsonium iodide (2) were synthesized. They showed similar reactivities compared with the free arsonium salts in the arsa-Wittig reaction. The use of the polymer-supported reagents facilitated product purification and rendered the organoarsenic reagents easily separable and recyclable.
- Lau, Kelvin C.Y.,Chiu, Pauline
-
experimental part
p. 8769 - 8774
(2011/12/02)
-
- An efficient phosphine-free heck reaction in water using Pd(l -Proline)2 as the catalyst under microwave irradiation
-
The present report describes an efficient and simple protocol for phosphine-free Heck reactions in water using a Pd(l-proline)2 complex as the catalyst under controlled microwave irradiation conditions. This methodology is versatile and provides excellent yields of products in short reaction times and minimizes costs, operational hazards and environmental pollution. Georg Thieme Verlag Stuttgart.
- Allam, Bharat Kumar,Singh, Krishna Nand
-
experimental part
p. 1125 - 1131
(2011/05/14)
-
- Facile regio- and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes: Selective hydrogenation of alkynes with formic acid
-
A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt3)4 (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt 3)4, but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Bronsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions.
- Shen, Ruwei,Chen, Tieqiao,Zhao, Yalei,Qiu, Renhua,Zhou, Yongbo,Yin, Shuangfeng,Wang, Xiangbo,Goto, Midori,Han, Li-Biao
-
supporting information; experimental part
p. 17037 - 17044
(2011/12/04)
-
- Ligand effects on Negishi couplings of alkenyl halides
-
Negishi couplings at olefinic centers do not always occur with the anticipated maintenance of stereochemistry. The source of erosion has been traced to the ligand, and a modified method has been developed that solves the stereochemical issue and significantly improves yields of Negishi couplings in general.
- Krasovskiy, Arkady,Lipshutz, Bruce H.
-
supporting information; experimental part
p. 3818 - 3821
(2011/10/01)
-
- The first example of hydrozirconation of alkynes in room temperature ionic liquids
-
Hydrozirconation of terminal alkynes in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) at 30 °C gave highly regio- and stereoselectively (E)-vinylzirconium complexes, which underwent a cross-coupling reaction with aryl halides in the presence of Pd(PPh 3)4 to afford (E)-1,2-disubstituted ethenes in good to high yields. Our system not only avoids the use of easily volatile THF or CH2Cl2 as solvent but also solves the basic problem of palladium catalyst reuse.
- Huang, Bin,Wang, Pingping,Hao, Wenyan,Cai, Ming-Zhong
-
experimental part
p. 2685 - 2688
(2011/07/09)
-
- 1,3,2,4-Diazadiphosphetidines as new P-N ligands for palladium-catalyzed Heck reaction in water
-
1,3,2,4-Diazadiphosphetidine-based phosphazane class have been used as a new generation of heterogeneous bidentate P(III) ligands containing nitrogen for base-free Pd(II) catalyzed C-C bond formation through Heck coupling reaction of aryl iodides, bromides and chlorides in water with styrene, n-butyl acrylate, 1-octene, and cyclohexene. The reactions occur heterogeneously in water and homogenously or partially heterogeneously in appropriate organic solvents. The ligand together with its Pd(0) complex is easily separated by filtration and reused for several runs.
- Iranpoor, Nasser,Firouzabadi, Habib,Tarassoli, Abbas,Fereidoonnezhad, Masood
-
supporting information; experimental part
p. 2415 - 2421
(2010/05/18)
-
- A highly tunable stereoselective olefination of semistabilized triphenylphosphonium ylides with N -Sulfonyl imines
-
The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph3PCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, α,β-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.
- Dong, De-Jun,Li, Hai-Hua,Tian, Shi-Kai
-
supporting information; experimental part
p. 5018 - 5020
(2010/06/13)
-
- Iron-catalyzed desulfinylative C-C cross-coupling reactions of sulfonyl chlorides with grignard reagents
-
(Chemical Equation Presented) A friendly couple: Conditions have been uncovered that allow the desulfinylative C-C cross-coupling reaction of inexpensive sulfonyl chlorides and Grignard reagents (see scheme, acac = acetylacetonate, NMP = N-methylpyrrolidone). The reactions rely on environmentally friendly iron catalysts and do not require expensive and/or toxic ligands.
- Rao Volla, Chandra M.,Vogel, Pierre
-
p. 1305 - 1307
(2008/12/22)
-
- Highly β-(E)-selective hydrosilylation of terminal and internal alkynes catalyzed by a (IPr)Pt(diene) complex
-
(Chemical Equation Presented) The regioselective hydrosilylation of terminal and internal alkynes catalyzed by the novel (IPr)Pt(AE) (7) (IPr = bis(2,6-diisopropylphenyl)imidazo-2-ylidene, AE = allyl ether) complex is presented. The (IPr)Pt(AE) catalyst displays enhanced activity and regioselectivity for the hydrosilylation of terminal and internal alkynes with low catalyst loading (0.1 to 0.05 mol %) when compared to the parent (IPr)Pt(DVDS) complex (6) (DVDS = divinyltetramethyldisiloxane). The reaction leads to exquisite regioselectivity in favor of the cis-addition product on the less hindered terminus of terminal and internal alkynes. The solvent effects were examined for the difficult hydrosilylation of benzylpropargyl ether. In light of the observed product distribution and kinetic data, a mechanistic scheme is proposed involving two competing catalytic cycles. One cycle leads to high regioselectivities while the other, having lost the stereodirecting IPr carbene ligand, displays low regiocontrol and activities. The importance of this secondary catalytic cycle is either caused by the strong coordinating ability of the alkyne or by the low reactivity of the silane or both.
- Berthon-Gelloz, Guillaume,Schumers, Jean-Marc,De Bo, Guillaume,Marko, Istvan E.
-
p. 4190 - 4197
(2008/09/20)
-
- Palladium-catalyzed hydrophenylation of alkynes with sodium tetraphenylborate under mild conditions
-
(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
-
p. 558 - 562
(2008/09/17)
-
- Manganese-catalyzed cross-coupling reaction between aryl grignard reagents and alkenyl halides
-
(Chemical Equation Presented) Aryl Grignard reagents react stereospecifically with alkenyl halides in the presence of manganese chloride (10%) to afford good yields of cross-coupling products.
- Cahiez, Gerard,Gager, Olivier,Lecomte, Fabien
-
supporting information; experimental part
p. 5255 - 5256
(2009/05/30)
-
- Vinyl tris(trimethylsilyl)silanes: substrates for Hiyama coupling
-
The oxidative treatment of vinyl tris(trimethylsilyl)silanes with hydrogen peroxide in aqueous sodium hydroxide in tetrahydrofuran generates reactive silanol or siloxane species that undergo Pd-catalyzed cross-couplings with aryl, heterocyclic, and alkenyl halides in the presence of Pd(PPh3)4 and tetrabutylammonium fluoride. Hydrogen peroxide and base are necessary for the coupling to occur while activation of the silanes with fluoride is not required. The conjugated and unconjugated tris(trimethylsilyl)silanes serve as good cross-coupling substrates. The (E)-silanes undergo coupling with retention of stereochemistry while coupling of (Z)-silanes occurred with lower stereoselectivity to produce an E/Z mixture of products.
- Wang, Zhizhong,Pitteloud, Jean-Philippe,Montes, Lucresia,Rapp, Magdalena,Derane, Djenny,Wnuk, Stanislaw F.
-
p. 5322 - 5327
(2008/09/21)
-
- Highly active Pd(II) catalysts with pyridylbenzoimidazole ligands for the Heck reaction
-
The air-, and thermo-stable palladium(II) complexes C1-C10 are prepared by the reaction of PdCl2(CH3CN)2 with pyridylbenzoimidazole. With various substituents on the pyridine ring, palladium atom was coordinated by two pyridylbenzoimidazole molecules via nitrogen atoms of benzoimidazole. The structure of complexes C3, C4, C6, and C7 has been confirmed by X-ray diffraction analysis. Without substituents on the pyridine ring, palladium atom was directly coordinated with two nitrogen atoms of pyridine and benzoimidazole nitrogen via intramolecular chelation (C10). These complexes performed the Heck olefination of aryl bromides in a good to high yield under phosphine-free conditions.
- Chen, Weixuan,Xi, Chanjuan,Wu, Yongwei
-
p. 4381 - 4388
(2008/02/13)
-
- Palladium-tetraphosphine catalysed heck reaction with simple alkenes: Influence of reaction conditions on the migration of the double bond
-
The Heck reaction of aryl halides with simple alk-1-enes is a powerful method for the synthesis of (E)-1-arylalk-1-ene derivatives. The major problem of this reaction is the palladium-catalysed migration of the carbon-carbon double bond along the alkyl ch
- Fall, Yacoub,Berthiol, Florian,Doucet, Henri,Santelli, Maurice
-
p. 1683 - 1696
(2008/02/08)
-
- An efficient palladium-catalyzed Heck coupling of aryl chlorides with alkenes
-
Catalyst system PdCl2(PCy3)2/Cs 2CO3 in dioxane was found to be the efficient catalyst system for Heck cross-coupling reactions of deactivated, neutral, and activated aryl chlorides with a variety of alkenes under mild conditions to afford selectively E-arylated alkenes in good to excellent yields.
- Yi, Chenyi,Hua, Ruimao
-
p. 2573 - 2576
(2007/10/03)
-
- Cobalt- and rhodium-catalyzed cross-coupling reaction of allylic ethers and halides with organometallic reagents
-
Reactions of 2-alkenyl methyl ether with phenyl, trimethylsilylmethyl, and allyl Grignard reagents in the presence of cobalt(II) complexes are discussed. The success of the reactions heavily depends on the combination of the substrate, ligand, and Grignard reagent. In the reaction of cinnamyl methyl ether, the formation of the linear coupling products predominates over that of the relevant branched products. In the cobalt-catalyzed allylation of allylic ethers, addition of a diphosphine ligand can change the regioselectivity, mainly providing the corresponding branched products. Rhodium complexes catalyze the reactions of allylic ethers and halides with allylmagnesium chloride and allylzinc bromide, respectively, in which the branched coupling product is the major product.
- Yasui, Hiroto,Mizutani, Keiya,Yorimitsu, Hideki,Oshima, Koichiro
-
p. 1410 - 1415
(2007/10/03)
-
- Cobalt-catalyzed allylic substitution reaction of allylic ethers with phenyl and trimethylsilylmethyl grignard reagents
-
Treatment of cinnamyl methyl ether with phenylmagnesium bromide in ether in the presence of CoCl2[1,5-bis(diphenylphosphino)pentane] affords 1,3-diphenylpropene in good yield. Similar allylic substitution reaction with trimethylsilylmethylmagne
- Mizutani, Keiya,Yorimitsu, Hideki,Oshima, Koichiro
-
p. 832 - 833
(2007/10/03)
-
- Cobalt(I)-catalyzed stereoselective olefination of alkylzinc reagents with aldehydes
-
The efficient olefination from organozinc reagents with aldehydes is exploited in a new synthesis of aryl and alkyl olefins.
- Wang, Jin-Xian,Fu, Ying,Hu, Yulai,Wang, Kehu
-
p. 1506 - 1510
(2007/10/03)
-