- Kinetic resolution in Pd-catalyzed allylic substitution using the helical PHelix ligand
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The chiral helical diphosphine 2,15-bis(diphenylphosphino)-hexahelicene (PHelix) is an excellent ligand in palladium catalyzed kinetic resolution involving allylic substitution. Depending upon the substrate, enantioselectivities (ee) of up to 99% are observed. Although formally a diphosphine, PHelix appears not to undergo chelation, which means that it behaves as a chiral monophosphine.
- Reetz, Manfred T.,Sostmann, Stefan
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- Enantioselective molybdenum-catalyzed allylic alkylation using chiral bisoxazoline ligands
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(equation presented) 54-86% yield R = Ph, Pr, CH3, OCH3, OPh 76 to 99% ee of A A : B = 8 : 1 up to >20 : 1 A series of chiral C2-symmetric bisoxazolines with trans-1,2-diaminocyclohexane backbones was synthesized. In view
- Glorius, Frank,Pfaltz, Andreas
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- Metallated Container Molecules: A Capsular Nickel Catalyst for Enhanced Butadiene Polymerisation
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A unique, covalently constructed capsular catalyst obtained by reaction of [Ni(η5-C5H5)(1,5-cyclooctadiene)] BF4 with the double-calixarene-derived diphosphine 1,3-bis(5-diphenylphosphino-25,26,27,28-tetrapropoxycalix[4]aren-17-yl)benzene (1) has been shown to polymerise butadiene at a rate considerably superior to that of previously known catalysts. The reported results indicate that the container structure of the covalent complex is retained during catalysis.
- Elaieb, Fethi,Sameni, Soheila,Awada, Mouhamad,Jeunesse, Catherine,Matt, Dominique,Toupet, Loic,Harrowfield, Jack,Takeuchi, Daisuke,Takano, Shigenaga
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- Derivatives of 2-amino-2′-diphenylphosphino-1,1′-binaphthyl (MAP) and their application in asymmetric palladium(O) -catalyzed allylic substitution
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CR)-(+)-2-Amino-2′-hydroxy-1,1′-binaphthyl (NOBIN, 5) can be readily converted into a series of novel N,N-disubstituted aminophosphines 9 and 23-25. The N,N-dimethyl derivative (R)-9 (MAP) was prepared via a sequence involving reductive alkylation with CH2O and NaBH4 (5 → 6), Pd-(0)-catalyzed coupling of the corresponding triflate with Ph2P(O)H (7 → 8), and reduction of the resulting phosphine oxide with Cl3SiH (8 → 9). Variation of this scheme was required for the preparation of 23-25 as the phosphinylation failed in the presence of bulky N substituents; the N-protected triflate 17 was first coupled with Ph2P(O)H, and the resulting phosphine oxide 18 was reduced with ClaSiH to give the aminophosphine 19, which was then subjected to reductive alkylation with individual ketones and NaBH4. The new P,N-binaphthyls thus obtained (23-25 and 9) were utilized as chiral ligands in Pd(0)-catalyzed allylic substitution. The enantioselectivites obtained for racemic 1,3-diphenylprop-2-en-l-yl acetate (±)-26 and malonate nucleophiles, which gave (S)-(-)-28, (-)-(+)-29, and (A)-(+)-30 as the respective products (in up to 71-73% ee at room temperature with Cs2CO3 in C2Cl2s and 9 or 23 as a ligand), are interpreted in terms of the chelated transition state 37 and preferential attack at the allylic terminus that is trans with respect to the phosphorus acceptor atom.
- Vyskocil, Stepan,Smrcina, Martin,Hanus, Vladimir,Polasek, Miroslav,Kocovsky, Pavel
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- Furanoside thioether-phosphinite ligands for Pd-catalyzed asymmetric allylic substitution reactions: Scope and limitations
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A series of readily available thioether-phosphinite ligands has been tested in the Pd-catalyzed allylic substitution reactions of several acyclic and cyclic allylic substrates (S1-S7). This series of ligands have been designed to uncover their important s
- Diéguez, Montserrat,Pàmies, Oscar,Claver, Carmen
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- Enantioselective allylic substitution, of cinnamyl esters catalyzed by iridium - Chiral aryl phosphite complexs conspicuous change in the mechanistic spectrum by a countercation and solvent
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Indium-catalyzed asymmetric allylic alkylation of monoaryl substrates 4-6 with chiral phosphites 1-3 has been investigated. Although branched isomers were formed with high regioselectivities, the enantioselectivities of these products were remarkably influenced by solvents, countercations, and additives (ZnCl2 and LiCl).
- Kinoshita, Naosumi,Marx, Karsten H.,Tanaka, Kiyoshi,Tsubaki, Kazunori,Kawabata, Takeo,Yoshikai, Naohiko,Nakamura, Eiichi,Fuji, Kaoru
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- New phosphite-oxazoline ligands for efficient Pd-catalyzed substitution reactions
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We have designed and synthesized a new family of readily available highly modular phosphite-oxazoline ligands for the Pd-catalyzed asymmetric allylic substitution reactions. The introduction of a π-acceptor flexible bulky biphenyl phosphite moiety in the ligand design is highly adventitious in the product outcome. Thus, this ligand series affords excellent reaction rates (TOF's up to >2400 mol·(mol·h)-1) and enantioselectivities (ee's up to >99%) and, at the same time, shows a broad scope for different substrate types. Copyright
- Pamies, Oscar,Dieguez, Montserrat,Claver, Carmen
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- Very efficient phosphoramidite ligand for asymmetric iridium-catalyzed allylic alkylation
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(Chemical Equation Presented) Linear or branched allylic carbonates or acetates undergo enantioselective iridium-catalyzed allylic substitution with sodium malonate. The reaction is wide in scope and affords the branched product in high yield and with hig
- Alexakis, Alexandre,Polet, Damien
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- Expanding the scope of the elpaN-type library: Glucose-derived bis(pyridine-2-carboxamide) ligands (elpaN-Py) for molybdenum-catalyzed asymmetric allylic alkylations
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The elpaN-Py family of ligands, which represents a subset of the elpaN-type library based on d-glucose, is described. The ligands are structural analogs of the privileged bis(pyridine-2-carboxamides) derived from trans-1,2- diaminocyclohexane, and differ
- Lega, Matteo,Figliolia, Rosario,Moberg, Christina,Ruffo, Francesco
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- A highly regioselective salt-free iron-catalyzed allylic alkylation
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(Chemical Equation Presented) Ironing out the kinks: A highly regioselective allylic alkylation can be performed in the presence of catalytic amounts of an iron(-II) complex and triphenylphosphane (see scheme; EWG = electron-withdrawing group). Allyl carbonates and pronucleophiles are coupled in high yields with a high regioselectivity comparable only with that obtained with Rh catalysts. The reaction is broadly applicable and does not require external base.
- Plietker, Bernd
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- First enantioselective alkylations of monosubstituted allylic acetates catalyzed by chiral iridium complexes
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Monoaryl allylic acetates were alkylated with sodium dimethylmalonate in the presence of iridium complexes of chiral phosphinooxazolines as catalysts to give branched products regioselectively in excellent yields with up to 95 % ee.
- Janssen, Joerg P.,Helmchen, Guenter
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- Enantioselective allylic substitution catalyzed by an iridium complex: Remarkable effects of the counter cation
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Allylic substitution of a methyl carbonate of cinnamyl alcohol with the anion of dimethyl malonate gave the branched olefin with high enantioselectivity in the presence of (S)-1,1'-binaphthyl-2,2'-diyl phenyl phosphite when a combination of lithium and zinc was used as counter cation.
- Fuji, Kaoru,Kinoshita, Naosumi,Tanaka, Kiyoshi,Kawabata, Takeo
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- Palladium catalysed allylic substitution via in situ activation of allylic alcohols
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In-situ activation of a variety of allylic alcohols by hexachlorophosphazene (or oxalyl chloride) followed by Pd(0) catalysed reactions with lithio dimethyl malonate leads to the regio and steroselective alkylations in god yields.
- Kumareswaran,Vankar, Yashwant D.
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- Rhodium-Catalyzed Stereoselective Intramolecular [5 + 2] Cycloaddition of 3-Acyloxy 1,4-Enyne and Alkene
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The first rhodium-catalyzed intramolecular [5 + 2] cycloaddition of 3-acyloxy 1,4-enyne and alkene was developed. The cycloaddition is highly diastereoselective in most cases. Various cis-fused bicyclo[5.3.0]decadienes were prepared stereoselectively. The chirality in the propargylic ester starting materials could be transferred to the bicyclic products with high efficiency. Electron-deficient phosphine ligand greatly facilitated the cycloaddition. Up to three new stereogenic centers could be generated. The resulting diene in the products could be hydrolyzed to enones, which allowed the introduction of more functional groups to the seven-membered ring.
- Shu, Xing-Zhong,Schienebeck, Casi M.,Li, Xiaoxun,Zhou, Xin,Song, Wangze,Chen, Lianqing,Guzei, Ilia A.,Tang, Weiping
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- Ruthenium-catalyzed allylic alkylation reactions: Carbonate-based catalysts and intermediates
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(Chemical Equation Presented) Branching out: A previously unrecognized ruthenium carbonate intermediate is formed during the reaction of an allylic tert-butoxycarbonate with the ruthenium complex [Ru(Cp*) (CH 3CN)3]PF6 (1;
- Hermatschweiler, Rene,Fernandez, Ignacio,Breher, Frank,Pregosin, Paul S.,Veiros, Luis F.,Calhorda, Maria Jose
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- Asymmetric molybdenum(0)-catalyzed allylic substitution
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Application of new ligands (R)-(-)-8,(S)-(+)-16, and (S)-(+)-17 to the title reaction (1 or 2 → 3) led to excellent regio- and enantioselectivities (> 30:1; ≤ 98% ee); although lacking the C2-symmetry, the catalysts can be viewed as quasi-C2-symmetrical since the single chiral center is sufficient to determine the sense of wrapping of the metal by the ligand.
- Malkov, Andrei V.,Spoor, Paul,Vinader, Victoria,Ko?ovsky, Pavel
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- High enantioselectivity in rhodium-catalyzed allylic alkylation of 1-substituted 2-propenyl acetates
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(Matrix presented) Rhodium-catalyzed asymmetric allylic alkylation of 1-substituted 2-propenyl acetates with dimethyl malonate proceeded with high enantioselectivity in the presence of cesium carbonate as a base and a rhodium catalyst generated from Rh(dp
- Hayashi, Tamio,Okada, Atsushi,Suzuka, Toshimasa,Kawatsura, Motoi
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- Constructing Mononuclear Palladium Catalysts by Precoordination/Solvothermal Polymerization: Recyclable Catalyst for Regioselective Oxidative Heck Reactions
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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
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supporting information
p. 2448 - 2453
(2019/02/03)
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- trans-Cyclooctenes as Halolactonization Catalysts
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The strained olefins in trans-cyclooctenes serve as efficient catalysts for halolactonizations, including bromolactonizations and iodolactonizations. The trans-cyclooctene framework is essential for excellent catalytic performance, and the substituents also play important roles in determining efficiency. These results are the first demonstration of catalysis by a trans-cyclooctene.
- Einaru, Shunsuke,Shitamichi, Kenta,Nagano, Tagui,Matsumoto, Akira,Asano, Keisuke,Matsubara, Seijiro
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supporting information
p. 13863 - 13867
(2018/09/27)
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- Metal-free, regio- and stereoselective synthesis of linear (E)-allylic compounds using C, N, O, and S nucleophiles
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A variety of allylic acetates and derivatives were synthesized by an efficient two-step protocol that employs readily available terminal alkenes as starting materials. This method is highly regio- and stereoselective, affording the linear (E)- isomer as the sole adduct. This process tolerates several functional groups including halogen-containing molecules, and it is general for weak oxygen, carbon, nitrogen, and sulfur nucleophiles. Furthermore, adducts were obtained in good to excellent yields.
- Huang, Xiaojun,Fulton, Brandon,White, Kana,Bugarin, Alejandro
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p. 2594 - 2597
(2015/06/16)
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- Palladium-catalyzed enantioselective allylic substitution in the presence of monodentate furanoside phosphoramidites
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A library of monodentate furanoside phosphoramidites, easily synthesized from inexpensive D-xylose and optically pure 1,1-bi-2-naphthol (BINOL), was used as ligands for the palladium-catalyzed allylic alkylation and amination. The matched pair was formed from D-xylose-derivatives and (S)-BINOL. The asymmetric induction depends strongly on the substituent at the C5 of the carbohydrate backbone; both bulky 5-O-pivaloyl and 5-deoxy derivatives gave excellent results, whereas ligands with trityl protection at position C5 induced low ee values with reversal of configuration. The solvent used for the addition is also of great importance with highest enantioselectivities observed in diethyl ether. The best results for both alkylation and amination, up to 98-99 ee, were obtained for sterically demanding allylic acetates. Single is better: New carbohydrate ligands bearing a single 1,1-bi-2-naphthol (BINOL)-derived phosphoramidite moiety are developed and successfully applied to the palladium-catalyzed asymmetric allylic substitution. The enantioselectivities are equal or better than those obtained for similar systems containing two BINOL moieties and reach up to 99 ee.
- Majdecki, Maciej,Jurczak, Janusz,Bauer, Tomasz
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p. 799 - 807
(2015/03/14)
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- Ruthenium-catalyzed regioselective allylic trifluoromethylthiolation reaction
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An efficient Ru-catalyzed regioselective allylic trifluoromethylthiolation reaction of allylic carbonates was developed. The linear allylic trifluoromethyl thioethers were obtained in 52-91% yields. Mechanistic investigation revealed that this reaction proceeds via a double allylic trifluoromethylthiolation sequence.
- Ye, Ke-Yin,Zhang, Xiao,Dai, Li-Xin,You, Shu-Li
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p. 12106 - 12110
(2015/01/09)
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- Chemo-, regio- and stereoselective heck arylation of allylated malonates: Mechanistic insights by ESI-MS and synthetic application toward 5-arylmethyl-γ-lactones
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We describe herein a general method for the controlled Heck arylation of allylated malonates. Both electron-rich and electron-poor aryldiazonium salts were readily employed as the aryl-transfer agents in good yields and in high chemo-, regio-, and stereoselectivity without formation of decarboxylated byproducts. Reaction monitoring via ESI-MS was used to support the formation of chelated Pd species through the catalytic cycle. Additionally, some Heck adducts were successfully used in the total synthesis of pharmacologically active γ-lactones.
- Oliveira, Caio C.,Marques, Marcelo V.,Godoi, Marla N.,Regiani, Thas,Santos, Vanessa G.,Santos, Emerson A.F. Dos,Eberlin, Marcos N.,S, Marcus M.,Correia, Carlos R.D.
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supporting information
p. 5180 - 5183
(2014/12/11)
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- Catalytic olefin hydroamination with aminium radical cations: A photoredox method for direct C-N bond formation
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While olefin amination with aminium radical cations is a classical method for C-N bond formation, catalytic variants that utilize simple 2° amine precursors remain largely undeveloped. Herein we report a new visible-light photoredox protocol for the intramolecular anti-Markovnikov hydroamination of aryl olefins that proceeds through catalytically generated aminium radical intermediates. Mechanistic studies are consistent with a process involving amine oxidation via electron transfer, turnover-limiting C-N bond formation, and a second electron transfer step to reduce a carbon-centered radical, rendering the overall process redox-neutral. A range of structurally diverse N-aryl heterocycles can be prepared in good to excellent yields under conditions significantly milder than those required by conventional aminium-based protocols.
- Musacchio, Andrew J.,Nguyen, Lucas Q.,Beard, G. Hudson,Knowles, Robert R.
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supporting information
p. 12217 - 12220
(2014/12/09)
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- Highly Enantioselective Alkylation of Allyl Acetates Using Tartrate-Derived Bioxazoline Ligands
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Tartrate-derived bioxazoline ligands, which form a five-membered chelate ring with metals, were evaluated for use in the asymmetric allylic alkylation (AAA) reactions of various symmetrical and unsymmetrical allyl acetates. Excellent enantioselectivities were achieved by using both symmetrical and unsymmetrical allyl acetates. Palladium(II)-catalyzed asymmetric allylic alkylation reactions of various symmetrical and unsymmetrical allyl acetates were achieved by using bioxazoline ligands, which were derived from tartaric acid, to give products with excellent enantioselectivity.
- Jayakumar, Samydurai,Prakash, Muthuraj,Balaraman, Kaluvu,Kesavan, Venkitasamy
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p. 606 - 615
(2015/10/05)
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- Bis(perfluoroalkyl) phosphino-oxazoline: A modular, stable, strongly π-accepting ligand for asymmetric catalysis
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A new class of stable, strongly π-accepting and modular bis-(perfluoroalkyl)-phosphine-oxazoline ligands (FOX) as CO mimics was prepared. It was demonstrated that these ligands, when coordinated to palladium catalysts, promote the asymmetric alkylation of monosubstituted allyl substrates with excellent regio- and enantioselectivity. Solid and solution structure analysis of the FOX-ligated Pd-allyl intermediate reveals that the combination of relative steric and strong trans influences presented by the P(CF 3)2 moiety gave rise to the excellent selectivity.
- Hu, Zongjian,Li, Yuguang,Liu, Kai,Shen, Qilong
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p. 7957 - 7967
(2013/01/15)
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- Achieving chemo-, regio-, and stereoselectivity in palladium-catalyzed reaction of γ-borylated allylic acetates
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Three-carbon highly functionalized γ-borylated allylic acetates underwent a regio- and stereocontrolled Tsuji-Trost reaction in the presence of palladium complexes. An ipso substitution of the acetate with complete stereoretention of the chiral center was achieved, leading to vinylic boronates with enantiomeric excesses above 99%.
- Kukkadapu, Krishna Kishore,Ouach, Aziz,Lozano, Pedro,Vaultier, Michel,Pucheault, Mathieu
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p. 4132 - 4135
(2011/10/02)
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- Palladium-catalyzed allylic substitution with (η6-Arene- CH2Z)Cr(CO)3-based nucleophiles
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Although the palladium-catalyzed Tsuji-Trost allylic substitution reaction has been intensively studied, there is a lack of general methods to employ simple benzylic nucleophiles. Such a method would facilitate access to "α-2-propenyl benzyl" motifs, which are common structural motifs in bioactive compounds and natural products. We report herein the palladium-catalyzed allylation reaction of toluene-derived pronucleophiles activated by tricarbonylchromium. A variety of cyclic and acyclic allylic electrophiles can be employed with in situ generated (η6-C 6H5CHLiR)Cr(CO)3 nucleophiles. Catalyst identification was performed by high throughput experimentation (HTE) and led to the Xantphos/palladium hit, which proved to be a general catalyst for this class of reactions. In addition to η6-toluene complexes, benzyl amine and ether derivatives (η6-C6H5CH 2Z)Cr(CO)3 (Z = NR2, OR) are also viable pronucleophiles, allowing C-C bond-formation α to heteroatoms with excellent yields. Finally, a tandem allylic substitution/demetalation procedure is described that affords the corresponding metal-free allylic substitution products. This method will be a valuable complement to the existing arsenal of nucleophiles with applications in allylic substitution reactions.
- Zhang, Jiadi,Stanciu, Corneliu,Wang, Beibei,Hussain, Mahmud M.,Da, Chao-Shan,Carroll, Patrick J.,Dreher, Spencer D.,Walsh, Patrick J.
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supporting information; experimental part
p. 20552 - 20560
(2012/02/13)
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- Better performance of monodentate P-stereogenic phosphanes compared to bidentate analogues in Pd-catalyzed asymmetric allylic alkylations
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The cationic allylpalladium complexes 3a-3f, 4a, 4e, 5e of type [Pd(η3-2-Me-C3H4)P2]PF 6 were synthesized using a group of monodentate P-stereogenic phosphanes, P=PPhRR' (a-f) and diphosphanes (PhRPCH2)2 (1a, 1e) or PhRPCH2Si(Me)2CH2PPhR (2e). The analogous cationic complexes with the disubstituted allyl group (η3-1,3-Ph2-C3H3) and monodentate phosphanes were not isolated as stable solids: only [PdCl(η3-1,3-Ph2-C3H3)P] (6a, 6d) were obtained. Palladium allyl complexes were screened as precatalysts in the allylic substitution of rac-3-acetoxy-1,3-diphenyl-1-propene (I) and (E)-3-acetoxy-1-phenyl-1-propene (III) with dimethyl malonate as the nucleophile. The various catalytic precursors showed a wide range of activity and selectivity. The bismonodentate phosphane complexes 3 are more active than the bidentate analogues. With regard to the regioselectivity, precursors containing monodentate phosphanes favour the formation of the linear product in the allylic substitution of cinnamyl acetate (III) compared with those containing bidentate phosphanes. With substrate I, compounds with the diphosphanes 1a and 1e, containing a five-membered chelate ring, gave low enantioselectivities (less than 10% ee), but those with the diphosphane 2e, forming a six-membered chelate ring or with two monodentate phosphanes, afforded products with moderate enantioselectivity under standard conditions (ee up to 74 %). The results show that the performance of precursors containing monodentate phosphanes was superior to those containing bidentate ligands in both activity and selectivity.
- Grabulosa, Arnald,Muller, Guillermo,Ceder, Rosa,Maestro, Miguel Angel
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scheme or table
p. 3372 - 3383
(2011/01/07)
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- Norbornene bidentate ligands: coordination chemistry and enantioselective catalytic applications
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N- and P-donor derivatives have been prepared by functionalization of a readily available norbomene precursor. Palladium, catalytic systems containing these new ligands were applied in allylic substitution, and yielded high, activities and excellent enantioselectivities for the allylic alkylation and amination reactions (ee up to 97%). A full coordination analysis of the catalytic precursors including modelling studies was also carried, out.
- Fernandez, Fernando,Gual, Aitor,Claver, Carmen,Castillon, Sergio,Muller, Guillermo,Gomez, Montserrat
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experimental part
p. 758 - 766
(2010/06/12)
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- Enantiomerically Pure P,N Chelates Based on Phospholene Rings: Palladium Complexes and Catalytic Applications in Allylic Substitution
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The synthesis of optically pure 2-pyridylphospholene ligands by diastereomeric resolution of PdII complexes, bearing the corresponding racemic P,N ligand and (R)-α-methylbenzylamine, by means of fractional, crystallisation is described. A full coordination study of palladium complexes containing 2pyridylphospholene and the corresponding phosphole ligands, both in solution (by means of NMR spectroscopy) and in the solid state (by X-ray diffraction), was carried out. These ligands were evaluated, in Pd-catalysed allylic substitution of racemic substrates (rac-3-acetoxy-l,3- diphenyl-l-propene and rac-3-acetoxy-l-cyclohexene) and (E)-3-acet-oxy-1-phenyl- 1-propene. A modelling study of the palladium allylic intermediates was performed, in order to justify the asymmetric induction observed with the 2-pyridylphospholene ligands.
- Leca, Francois,Fernandez, Fernando,Muller, Guillermo,Lescop, Christophe,Reau, Regis,Gomez, Montserrat
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scheme or table
p. 5583 - 5591
(2010/06/15)
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- Features and applications of [Rh(CO)2Cl]2-catalyzed alkylations of unsymmetrical allylic substrates
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(Chemical Equation Presented) A novel regio- and stereoselective [Rh(CO)2Cl]2-catalyzed allylic alkylation of unsymmetrical allylic carbonates was discovered. The regioselectivity of the reaction favors product ratios in which substitution occurs at the carbon bearing the leaving group. When an enantiomerically enriched carbonate (≥99% ee) was examined, the Rh(I)-catalyzed allylic alkylation proceeded stereoselectively to provide the alkylation product with retention of absolute stereochemistry (98% ee). To establish the scope of the [Rh(CO)2Cl]2-catalyzed allylic alkylation, a variety of carbon and heteroatom nucleophiles were examined and the results described. As an application of the Rh(I)-catalyzed allylic alkylation, a series of novel domino reactions have been developed that couple the unique regio- and stereoselective [Rh(CO)2Cl]2- catalyzed alkylation of allylic trifluoroacetates with an intramolecular Pauson-Khand annulation, a cycloisomerization, or a [5+2] cycloaddition. A unique aspect of the method described is the use of a single catalyst to effect sequential transformations in which the catalytic activity is moderated simply by controlling the reaction temperature. Implementation of such processes provides a rapid and efficient entry to a variety of bicyclic carbon skeletons from simple precursors.
- Ashfeld, Brandon L.,Miller, Kenneth A.,Smith, Anna J.,Tran, Kristy,Martin, Stephen F.
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p. 9018 - 9031
(2008/03/13)
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- First allylpalladium systems containing chiral imidazolylpyridine ligands - Structural studies and catalytic behaviour
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Palladium/chiral imidazolylpyridine systems were tested in allylic alkylation of rac-3-acetoxy-1,3-diphenyl-1-propene (rac-I) and 3-acetoxy-1-phenyl-1-propene (II), paying particular attention to the influence of the amine nitrogen hybridisation on their catalytic behaviour. Allylpalladium complexes 9-11 containing optically pure imidazolines were synthesised and fully characterised both in solution (NMR) and the solid state (single-crystal X-ray diffraction). NMR studies showed four species in solution for complex 9 containing the unsymmetrical 1-phenylallyl group, while for 10 and 11, involving the symmetrical 1,3-diphenylallyl moiety, two species, endo and exo, were identified. In the solid state, only endo isomers crystallised for each complex. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Bastero, Amaia,Bella, Antonio F.,Fernandez, Fernando,Jansat, Susanna,Claver, Carmen,Gomez, Montserrat,Muller, Guillermo,Ruiz, Aurora,Font-Bardia, Merce,Solans, Xavier
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p. 132 - 139
(2007/10/03)
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- Gold(I)-catalyzed [2 + 2]-cycloaddition of allenenes
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A cationic phosphinegold(I)-catalyzed intramolecular [2 + 2]-cycloaddition between an allene and an alkene to form alkylidene?cyclobutanes is described. Additionally, the reported cycloisomerization reaction provides access to enantioenriched bicyclo-[3.2.0] structures using chiral biarylphosphinegold(I) complexes as catalysts. Copyright
- Luzung, Michael R.,Mauleon, Pablo,Toste, F. Dean
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p. 12402 - 12403
(2008/09/17)
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- Enantioselective Iridium-catalyzed allylic alkylations - Improvements and applications based on salt-free reaction conditions
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Simplified procedures for the Ir-catalyzed asymmetric allylic alkylation reaction are described that often allow substitution products to be obtained with ≥99% ee. Applications to syntheses of important chiral building blocks, such as the Taniguchi lacton
- Gnamm, Christian,F?rster, Sebastian,Miller, Nicole,Br?dner, Kerstin,Helmchen, Günter
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p. 790 - 794
(2007/12/29)
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- Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxides: DIAPHOXs. Formal enantioselective synthesis of (-)-paroxetine
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An Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxide is described. Asymmetric allylic alkylation of terminal allylic carbonates proceeded using 5 mol % of Ir catalyst, 5 mol % of DIAPHOX 1i, 10 mol % of NaPF6, 10 mo
- Nemoto, Tetsuhiro,Sakamoto, Tatsurou,Fukuyama, Takashi,Hamada, Yasumasa
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p. 4977 - 4981
(2008/02/09)
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- Allylic alkylation and amination using mixed (NHC)(phosphine) palladium complexes under biphasic conditions
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A dramatic improvement of the catalytic activity was observed when a phosphine was added in allylic alkylation reactions catalyzed by (NHC)Pd(η3-C3H5)Cl complexes. Consequently, several palladium complexes, generated in situ from different NHC-silver complexes, [Pd(η3-C3H5)Cl]2 and PPh3, were tested in this reaction to evaluate their potential. High reaction rates and conversions could be obtained with this catalytic system in the alkylation of allylic acetates with dimethylmalonate, particularly under biphasic conditions using water/dichloromethane and KOH 1 M as the base. These conditions are experimentally more convenient and gave higher reaction rates than the classical anhydrous conditions (NaH/THF). In this system, the phosphine is essential since no conversion was obtained when it is not present. The steric hindrance of the carbene ligand has a great influence on the activity and the stability of the catalytic system. The best NHC ligands for this reaction are either 1-mesityl-3-methyl-imidazol-2-ylidene or 1-(2,6-diisopropylphenyl)-3-methyl-imidazol-2-ylidene which are less bulky among the NHC tested. These two ligands led in 5 min to a complete conversion at 20 °C. The Pd-catalyzed allylic amination reaction using (E)-1,3-diphenylprop-3-en-yl acetate and benzylamine was also tested with (NHC)(PPh3)Pd complexes and under the biphasic conditions. This reaction was found to be slower than the alkylation with dimethylmalonate but a complete conversion could be reached in 6 h at 20 °C using K2CO3 1 M as the base. NMR experiments indicated that mixed (NHC)(PPh3)Pd complexes are formed in situ but their structure could not be established exactly.
- Flahaut, Alexandre,Roland, Sylvain,Mangeney, Pierre
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p. 5754 - 5762
(2008/03/13)
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- Phosphoramidite ligands in iridium-catalyzed allvlic substitution
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A new phosphoramidite ligand was used in the iridium-catalyzed allylic substitution reaction. This permitted high regio- and enantioselectivities on a wide variety of substrates and nucleophiles. Because of the stereospecificity of the reaction obtained by using branched substrates, a kinetic resolution reaction was attempted. The origin of the impressive efficiency of this ligand in terms of kinetics was explored in detail, as was the role of the substituent in the ortho-position of the amine moiety.
- Polet, Damien,Alexakis, Alexandre,Tissot-Croset, Karine,Corminboeuf, Clemence,Ditrich, Klaus
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p. 3596 - 3609
(2008/02/04)
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- Regioselectivity with hemispherical chelators: Increasing the catalytic efficiency of complexes of diphosphanes with large bite angles
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(Chemical Equation Presented) Control through molecular pockets: Calixarene-derived diphosphites provide effective hemispherical crowding about catalytic centers. When used in the palladium-catalyzed alkylation of cinnamyl acetate, regioselectivities higher than 98% in favor of the linear product are observed. In the rhodium-catalyzed hydroformylation of styrene, these diphosphites lead to phenylpropionaldehyde with selectivities as high as 76%.
- Semeril, David,Jeunesse, Catherine,Matt, Dominique,Toupet, Loic
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p. 5810 - 5814
(2007/10/03)
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- Asymmetric allylic substitution catalyzed by C1-symmetrical complexes of molybdenum: Structural requirements of the ligand and the stereochemical course of the reaction
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Application of new chiral ligands (R)-(-)-12a and (S)-(+)-12c (VALDY), derived from amino acids, to the title reaction, involving cinnamyl (linear) and isocinnamyl (branched) type substrates (4 and 5 → 6), led to excellent regio- and enantioselectivities (>30:1, ≤98% ee), showing that ligands with a single chiral center are capable of high asymmetric induction. The structural requirements of the ligand and the mechanism are discussed. The application of single enantiomers of deuterium-labeled substrates (both linear 38c and branched 37c) and analysis of the products (41-43) by 2{ 1H) NMR spectroscopy in a chiral liquid crystal matrix allowed the stereochemical pathways of the reaction to be distinguished. With ligand (S)-(+)-12c, the matched enantiomer of branched substrate was found to be (S)-5, which was converted into (R)-6 with very high regio- and stereoselectivity via a process that involves net retention of stereochemistry. The mismatched enantiomer of the branched substrate was found to be (R)-5, which was also converted into (R)-6, that is, with apparent net inversion, but at a lower rate and with lower overall enantioselectivity. This latter feature, which may be termed a "memory effect", reduced the global enantioselectivity in the reaction of the racemic substrate (±)-5. The stereochemical pathway of the mismatched manifold has been shown also to be one of net retention, the apparent inversion occurring through equilibration via an Mo-allyl intermediate prior to nucleophilic attack. Incomplete equilibration leads to the memory effect and thus to lower enantioselectivity. Analysis of the mismatched manifold over the course of the reaction revealed that the memory effect is progressively attenuated with the nascent global selectivity increasing substantially as the reaction proceeds. The origin of this effect is suggested to be the depletion of CO sources in the reaction mixture, which attenuates turnover rate and thus facilitates greater equilibrium. The linear substrate was also converted into the branched product with net syn stereochemistry, as shown by isotopic labeling. An analogous process operates in the generation of small quantities of linear product from branched substrate.
- Malkov, Andrei V.,Gouriou, Laure,Lloyd-Jones, Guy C.,Stary, Ivo,Langer, Vratislav,Spoor, Paul,Vinader, Victoria,Kocovsky, Pavel
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p. 6910 - 6929
(2007/10/03)
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- Regioselective allylic alkylation and etherification catalyzed by in situ generated N-heterocyclic carbene ruthenium complexes
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Benzimidazolium halides are used for the first time as ligand precursors in ruthenium-catalyzed substitution of allylic carbonates and chlorides by carbon nucleophiles and phenols, respectively. After generation of diaminocarbene species upon deprotonatio
- Gürbüz, Nevin,?zdemir, Ismail,?etinkaya, Bekir,Renaud, Jean-Luc,Demerseman, Bernard,Bruneau, Christian
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p. 535 - 538
(2007/10/03)
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- Carbocycles via enantioselective inter- and intramolecular iridium-catalysed allylic alkylations
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Carbocycles with > 90% ee were prepared via Ir-catalysed asymmetric allylic alkylation/ring closing metathesis sequences or enantioselective Ir-catalysed intramolecular allylic alkylations. The Royal Society of Chemistry 2005.
- Streiff, Stephane,Welter, Carolin,Schelwies, Mathias,Lipowsky, Gunter,Miller, Nicole,Helmchen, Guenter
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p. 2957 - 2959
(2007/10/03)
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- α-Diimines as nitrogen ligands for ruthenium-catalyzed allylation reactions and related (pentamethylcyclopentadienyl) ruthenium complexes
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The new Cp*Ru(II) (Cp*: pentamethylcyclopentadienyl) complexes Cp*(dab-R)RuCl, [Cp*(dab-R)(MeCN)Ru][PF6] (dab-R: RNCH-CHNR; R: iso-propyl, mesityl), and [Cp*(cod)(MeCN)Ru][PF 6], are synthesized in high yields by reacting the corresp
- Mbaye, Mbaye D.,Demerseman, Bernard,Renaud, Jean-Luc,Bruneau, Christian
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p. 2149 - 2158
(2007/10/03)
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- N-Heterocyclic carbenes as ligands in palladium-catalyzed Tsuji-Trost allylic substitution
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A Pd(0)-catalyzed allylic substitution (i.e., Tsuji-Trost reaction) using N-heterocyclic carbene as a ligand was investigated. It has been proven that an imidazolium salt 2d having bulky aromatic rings attached to the nitrogens in its imidazol-2-ylidene skeleton is suitable as a ligand precursor and that a Pd2dba3-imidazolium salt 2d-Cs2CO3 system is highly efficient for producing a Pd-NHC catalyst in this reaction. Allylic substitution using a Pd-NHC complex differed from that using a Pd-phosphine complex as follows: (1) the reaction using a Pd-NHC complex required elevated temperature (50 °C or reflux in THF), (2) allylic carbonates were inert to a Pd-NHC complex, and (3) nitrogen nucleophiles such as sulfonamide and amine did not react with allylic acetate. It was also found that allylic substitution with a soft nucleophile using a Pd-NHC catalyst proceeds via overall retention of configuration to give the product in a stereospecific manner, the stereochemical reaction course obviously being the same as that of the reaction using a Pd-phosphine complex.
- Sato, Yoshihiro,Yoshino, Taro,Mori, Miwako
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p. 5753 - 5758
(2007/10/03)
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- Chiral bis(N-sulfonylamino)phosphine- and TADDOL-phosphite-oxazoline ligands: Synthesis and application in asymmetric catalysis
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A series of N,P-ligands has been prepared, containing a chiral oxazoline ring and as a second chiral unit a bis(N-sulfonylamino)phosphine group embedded in a diazaphospholidine ring or a cyclic phosphite group derived from TADDOL. These modular ligands are readily synthesized from chiral amino alcohols and chiral 1,2-diamines or TADDOLs. Palladium and iridium complexes derived from these ligands were found to be efficient catalysts for enantioselective allylic alkylation and olefin hydrogenation, respectively.
- Hilgraf, Robert,Pfaltz, Andreas
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- Conformational preferences and enantiodiscrimination of phosphino-4-(1-hydroxyalkyl)oxazoline-metal-olefin complexes resulting from an OH-metal hydrogen bond
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Phosphinooxazolines carrying (1-hydroxy-1-phenyl)methyl and (1-methoxy-1-phenyl)methyl substituents in the 4 position of the oxazoline ring exhibit contrasting behavior in Pd- and Ir-catalyzed allylic alkylations. Whereas catalysts with the methoxy-containing ligand generally provide products with high ee's, use of catalysts prepared from the hydroxy-containing ligand results in products with low ee's or even racemates. DFT calculations suggest the presence of a hydrogen bond with Pd(0) as the proton acceptor in the hydroxy-containing olefin-Pd(0) complexes, which induces a conformational change in the ligand, leading to different stereoselectivity.
- Froelander, Anders,Lutsenko, Serghey,Privalov, Timofei,Moberg, Christina
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p. 9882 - 9891
(2007/10/03)
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- Regio- and enantioselective iridium-catalyzed allylic alkylation with in situ activated P,C-chelate complexes
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Come together: Successful cooperation of iridium and copper yielded a new catalyst system for allylic alkylation. Branched alkylation products can be obtained rapidly and with high enantioselectivity from simple linear precursors (see scheme; cod = cycloo
- Lipowsky, Gunter,Miller, Nicole,Helmchen, Guenter
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p. 4595 - 4597
(2007/10/03)
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- Diastereomerism in palladium(II) allyl complexes of P,P-, P,S- and S,S-donor ligands, Ph2P(E)N(R)P(E′)Ph2 [R=CHMe2 or (S)-*CHMePh; E=E′=lone pair or S]: Solution behaviour, X-ray crystal structure and catalytic allylic alkylation reactions
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The reactions of achiral homodonor diphosphazane ligands, Ph2P(E)N(CHMe2)P(E′)Ph2 [E=E′=lone pair (1) or S (2)] with the chloro bridged palladium dimers, [Pd(η3-1,3-R′-R″-C3 H3)(μ-Cl)]2 (R′, R″=H, Me or Ph) in the presence of NH4PF6 give cationic η3-allyl palladium complexes, [Pd(η3-1,3-R′-R″-C3H3) (L-L′)]. Each of these complexes exists as single species in solution except the 1,3-dimethyl allyl complex, which exists as two isomers (syn/syn- and syn/anti-) in solution. Analogous allyl palladium complexes derived from the chiral homodonor diphosphazane ligand, Ph2PN((S)-*CHMePh)PPh2 (3) exist as a single species when the allyl moiety is symmetrical (R′=R″=H or Ph) but a 1:1 mixture of two different face-coordinated diastereomers if the allyl moiety is unsymmetrically substituted (R′≠R″). The 1,3-dimethyl-allyl complex, [Pd(η3-1,3-Me2-C3H3) {Ph2PN((S)-*CHMePh)PPh2-k2P,P}] PF6 (20) exists as a mixture of two isomers. The major isomer (20a) has the syn/syn -allylic arrangement while the minor isomer (20b) has the syn/anti configuration. These isomers (20a and 20b) equilibrate in solution via a syn-anti isomerisation pathway. Achiral and chiral heterodonor monosulphide ligands, Ph2P(S)N(R) PPh2 [R=CHMe2 (4), (S)-*CHMePh(5)] give rise to allyl palladium complexes which exist as several isomers in solution. The presence of a chiral centre in the ligand 5 enables the observation of two NMR distinguishable face-coordinated diastereomers for its allyl complexes. However, the solid state structure of [Pd(η3-C3H5){Ph2P(S) N((S)-*CHMePh)PPh2-k2 P,S}]PF6 (27) shows the presence of only one diastereomer. Two-dimensional (2D) phase sensitive 1H-1H NOESY and ROESY measurements indicate that the monosulphide complexes undergo exchange by the opening of the η3-allyl group selectively at the trans position with respect to the greater π-acceptor phosphorus centre to generate a η1-bonded intermediate. Preliminary studies on the use of the ligands 1-5 for catalytic allylic alkylation reactions of an unsymmetrically substituted substrate, (E)-1-phenyl-2-propenyl-acetate are reported.
- Mandal,Gowda, G.A. Nagana,Krishnamurthy, Setharampattu S.,Zheng, Chong,Li, Shoujian,Hosmane, Narayan S.
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- A structure-activity relationship for pincer palladium(II) complexes - Influence of ring-size of metallacycles on the activity in allylic alkylation
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A series of new palladium(II) complexes derived from the well-known pincer complex [PdCl{(C6H3)(OPi Pr2)2-2,6}] were synthesised: [PdX{(C6 H3)(OPiPr2)2-2,6}] (X = Br-, I-, OAc-, OTf-). A novel PCP′ pincer ligand 1-(iPr2 PO)-3-(iPr2POCH2)(C6 H4) was prepared and complexed to palladium(II) to give [PdX{(C6H3)(OPiPr2)-2- (CH2OPiPr2)-6}] (X=Cl-, I-, OAc-, OTf-, BF4 -). The X-ray structure of [PdCl{(C6H3) (OPiPr2)-2-(CH2OPi Pr2)-6}] was solved and is discussed. These complexes were applied to the catalytic reaction of cinnamyl acetate with sodium dimethyl malonate in order to evaluate the influence of the ligand structure and co-ordinating or non-co-ordinating anions on the regioselectivity. A detailed analysis shows that palladium(II) complexes of the unsymmetrical PCP′ bis(phosphinito) ligand are much more active when compared to related complexes of the symmetrical PCP bis(phosphinito) ligand. The origin of this difference in activity is discussed.
- Wang, Zhaohui,Eberhard, Michael R.,Jensen, Craig M.,Matsukawa, Shiro,Yamamoto, Yohsuke
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p. 189 - 195
(2007/10/03)
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- Ruthenium-bisimine: A new catalytic precursor for regioselective allylic alkylation
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New complexes [Cp*Ru(bisimine)Cl] are active catalysts for the regioselective alkylation of allylic carbonates by soft carbonucleophiles, in favour of the branched isomers. The catalysts can be conveniently prepared in situ from [Cp*Ru(cod)Cl] and a bulky aromatic bisimine.
- Renaud, Jean-Luc,Bruneau, Christian,Demerseman, Bernard
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p. 408 - 410
(2007/10/03)
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- Pd-catalyzed allylic substitution using nucleophilic N-heterocyclic carbene as a ligand
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(Matrix presented) A nucleophilic N-heterocyclic carbene has been successfully used in a Pd(0)-catalyzed allylic substitution for the first time. It was found that allylic substitution with a soft nucleophile using a Pd-carbene catalyst proceeds via retention of configuration, the stereochemical reaction pathway being the same as that of the reaction using a Pd-phosphine complex.
- Sato, Yoshihiro,Yoshino, Taro,Mori, Miwako
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- The Effect of Hydrogen Bonding on Allylic Alkylation and Isomerization Reactions in Ionic Liquids
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Neutral allylic alkylation reactions, in which a base is generated in situ and which hence require no external bases, can significantly be retarded when carried out in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]). Evidence suggests that the base or base precursor enters into hydrogen bonding with the imidazolium cation and is thus made less readily available for deprotonation of pre-nucleophiles. However, the reaction proceeds well in the presence of stronger bases that are capable of deprotonation. Whilst the phenomenon of hydrogen bonding in ionic liquids can be detrimental to reactions such as allylic alkylation, it can be exploited to suppress unwanted allylic isomerization.
- Ross, James,Xiao, Jianliang
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p. 4900 - 4906
(2007/10/03)
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- Iridium-catalysed allylic substitution: Stereochemical aspects and isolation of IrIII complexes related to the catalytic cycle
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Ir-catalysed allylic alkylations of enantiomerically enriched monosubstituted allylic acetates proceed with up to 87% retention of configuration using P(OPh)3 as ligand. High retention enantioselectivity of up to 86% ee in asymmetric allylic alkylations of achiral or racemic substrates is achieved with monodentate phosphorus amidites as ligands. Lithium N-tosylbenzylamide was identified as a suitable nucleophile for allylic aminations. Of particular importance is the use of lithium chloride as an additive, generally leading to increased enantioselectivities. Two (π-allyl)IrIII complexes were characterised by X-ray crystal structure analysis and spectroscopic data.
- Bartels, Bjoern,Garcia-Yebra, Cristina,Rominger, Frank,Helmchen, Guenter
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p. 2569 - 2586
(2007/10/03)
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- A stereospecific ruthenium-catalyzed allylic alkylation
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Good regioselectivity and chirality transfer for aryl-substituted allyl units is achieved in allylic alkylations with a wide range of nucleophiles by using the highly active ruthenium catalyst 1. This method provides a route to antidepressants such as (-)-fluoxetine from (S)-ephedrine (see scheme; Cp* = η5-C5Me5, TBAT = tetrabutylammonium triphenyldifluorosilicate).
- Trost, Barry M.,Fraisse, Pierre L.,Ball, Zachary T.
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p. 1059 - 1061
(2007/10/03)
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- Designed ligands as probes for the catalytic binding mode in Mo-catalyzed asymmetric allylic alkylation
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Unusual coordination in the asymmetric allylic alkylation catalyzed by molybdenum (see scheme) was revealed by a study on several ligands, for example, 1. Unexpectedly, only the nitrogen atom of one picolinamide group coordinates to Mo, while the other am
- Trost, Barry M.,Dogra, Kalindi,Hachiya, Iwao,Emura, Takashi,Hughes, David L.,Krska, Shane,Reamer, Robert A.,Palucki, Michael,Yasuda, Nobuyoshi,Reider, Paul J.
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p. 1929 - 1932
(2007/10/03)
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