- Stereoselective Iridium-N,P-Catalyzed Double Hydrogenation of Conjugated Enones to Saturated Alcohols
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Asymmetric hydrogenation of prochiral substrates such as ketones and olefins constitutes an important instrument for the construction of stereogenic centers, and a multitude of catalytic systems have been developed for this purpose. However, due to the different nature of the π-system, the hydrogenation of olefins and ketones is normally catalyzed by different metal complexes. Herein, a study on the effect of additives on the Ir-N,P-catalyzed hydrogenation of enones is described. The combination of benzamide and the development of a reactive catalyst unlocked a novel reactivity mode of Crabtree-type complexes toward C=O bond hydrogenation. The role of benzamide is suggested to extend the lifetime of the dihydridic iridium intermediate, which is prone to undergo irreversible trimerization, deactivating the catalyst. This unique reactivity is then coupled with C=C bond hydrogenation for the facile installation of two contiguous stereogenic centers in high yield and stereoselectivity (up to 99% ee, 99/1 d.r.) resulting in a highly stereoselective reduction of enones.
- Andersson, Pher G.,Krajangsri, Suppachai,Peters, Bram B. C.,Zheng, Jia
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- Highly Active Cooperative Lewis Acid—Ammonium Salt Catalyst for the Enantioselective Hydroboration of Ketones
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Enantiopure secondary alcohols are fundamental high-value synthetic building blocks. One of the most attractive ways to get access to this compound class is the catalytic hydroboration. We describe a new concept for this reaction type that allowed for exceptional catalytic turnover numbers (up to 15 400), which were increased by around 1.5–3 orders of magnitude compared to the most active catalysts previously reported. In our concept an aprotic ammonium halide moiety cooperates with an oxophilic Lewis acid within the same catalyst molecule. Control experiments reveal that both catalytic centers are essential for the observed activity. Kinetic, spectroscopic and computational studies show that the hydride transfer is rate limiting and proceeds via a concerted mechanism, in which hydride at Boron is continuously displaced by iodide, reminiscent to an SN2 reaction. The catalyst, which is accessible in high yields in few steps, was found to be stable during catalysis, readily recyclable and could be reused 10 times still efficiently working.
- Titze, Marvin,Heitk?mper, Juliane,Junge, Thorsten,K?stner, Johannes,Peters, René
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p. 5544 - 5553
(2021/02/05)
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- Kinetic Resolution of Allyltriflamides through a Pd-Catalyzed C-H Functionalization with Allenes: Asymmetric Assembly of Tetrahydropyridines
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Enantioenriched, six-membered azacycles are essential structural motifs in many products of pharmaceutical or agrochemical interest. Here we report a simple and practical method for enantioselective assembly of tetrahydropyridines, which is paired to a ki
- González, José Manuel,Cendón, Borja,Mascare?as, José Luis,Gulías, Moisés
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supporting information
p. 3747 - 3752
(2021/04/06)
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- Capturing the Monomeric (L)CuH in NHC-Capped Cyclodextrin: Cavity-Controlled Chemoselective Hydrosilylation of α,β-Unsaturated Ketones
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The encapsulation of copper inside a cyclodextrin capped with an N-heterocyclic carbene (ICyD) allowed both to catch the elusive monomeric (L)CuH and a cavity-controlled chemoselective copper-catalyzed hydrosilylation of α,β-unsaturated ketones. Remarkably, (α-ICyD)CuCl promoted the 1,2-addition exclusively, while (β-ICyD)CuCl produced the fully reduced product. The chemoselectivity is controlled by the size of the cavity and weak interactions between the substrate and internal C?H bonds of the cyclodextrin.
- Bistri-Aslanoff, Olivia,Derat, Etienne,Leloux, Sébastien,Leyssens, Tom,Ménand, Micka?l,Meijide Suárez, Jorge,Riant, Olivier,Roland, Sylvain,Sollogoub, Matthieu,Xu, Guangcan,Zhang, Pinglu,Zhang, Yongmin
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supporting information
p. 7591 - 7597
(2020/03/23)
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- Chemoselective Luche-Type Reduction of α,β-Unsaturated Ketones by Magnesium Catalysis
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The chemoselective reduction of α,β-unsaturated ketones by use of an economic and readily available Mg catalyst has been developed. Excellent yields for a wide range of ketones have been achieved under mild reaction conditions, short times, and low catalyst loadings (0.2-0.5 mol %).
- Jang, Yoon Kyung,Magre, Marc,Rueping, Magnus
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supporting information
p. 8349 - 8352
(2019/10/16)
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- CuH-Catalyzed Enantioselective Ketone Allylation with 1,3-Dienes: Scope, Mechanism, and Applications
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Chiral tertiary alcohols are important building blocks for the synthesis of pharmaceutical agents and biologically active natural products. The addition of carbon nucleophiles to ketones is the most common approach to tertiary alcohol synthesis but traditionally relies on stoichiometric organometallic reagents that are difficult to prepare, sensitive, and uneconomical. We describe a mild and efficient method for the copper-catalyzed allylation of ketones using widely available 1,3-dienes as allylmetal surrogates. Homoallylic alcohols bearing a wide range of functional groups are obtained in high yield and with good regio-, diastereo-, and enantioselectivity. Mechanistic investigations using density functional theory (DFT) implicate the in situ formation of a rapidly equilibrating mixture of isomeric copper(I) allyl complexes, from which Curtin-Hammett kinetics determine the major isomer of the product. A stereochemical model is provided to explain the high diastereo- and enantioselectivity of this process. Finally, this method was applied to the preparation of an important drug, (R)-procyclidine, and a key intermediate in the synthesis of several pharmaceuticals.
- Li, Chengxi,Liu, Richard Y.,Jesikiewicz, Luke T.,Yang, Yang,Liu, Peng,Buchwald, Stephen L.
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supporting information
p. 5062 - 5070
(2019/03/26)
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- Non-enzymatic acylative kinetic resolution of primary allylic amines
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A non-enzymatic acetyl transfer-based kinetic resolution of primary allylic amines is reported. The process involves the use of (1S,2S)-1 in conjunction with a supported ammonium salt and affords the corresponding enantio-enriched N-acetylated allylic ami
- Kolleth, Amandine,Cattoen, Martin,Arseniyadis, Stellios,Cossy, Janine
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supporting information
p. 9338 - 9340
(2013/10/01)
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- Highly stereoselective C-C bond formation by rhodium-catalyzed tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor carbenoids and chiral allylic alcohols
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The tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor rhodium carbenoids and chiral allyl alcohols is a convergent C-C bond forming process, which generates two vicinal stereogenic centers. Any of the four possible stereoisomers can be selectively synthesized by appropriate combination of the chiral catalyst Rh2(DOSP)4 and the chiral alcohol.
- Li, Zhanjie,Parr, Brendan T.,Davies, Huw M. L.
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supporting information; experimental part
p. 10942 - 10946
(2012/08/07)
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- Copper(i) catalyzed asymmetric 1,2-addition of Grignard reagents to α-methyl substituted α,β-unsaturated ketones
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The first catalytic enantioselective 1,2-addition of Grignard reagents to ketones is presented. This additive-free copper(i) catalyzed 1,2-addition provides chiral allylic tertiary alcohols with an er of up to 98:2 and excellent yields due to the complete shift of overwhelming 1,4-selectivity of copper(i)-catalysts towards 1,2-selectivity in the addition reaction to enones.
- Madduri, Ashoka V. R.,Minnaard, Adriaan J.,Harutyunyan, Syuzanna R.
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supporting information; scheme or table
p. 1478 - 1480
(2012/02/16)
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- CuH-catalyzed enantioselective 1,2-reductions of α,β-unsaturated ketones
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The first study on a general technology for arriving at valued nonracemic allylic alcohols using asymmetric ligand-accelerated catalysis by copper hydride is described.
- Moser, Ralph,Boskovia, Zarko V.,Crowe, Christopher S.,Lipshutz, Bruce H.
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supporting information; experimental part
p. 7852 - 7853
(2010/08/04)
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- Free-radical-initiated coupling reaction of alcohols and alkynes: Not co but C-C bond formation
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This work demonstrates an efficient method to prepare allylic alcohols via direct C-C bond formation using electron-rich alkynes and aliphatic alcohols initiated by tert-butyl hydroperoxide.
- Liu, Zhong-Quan,Sun, Liang,Wang, Jian-Guo,Han, Jie,Zhao, Yan-Kai,Zhou, Bo
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supporting information; scheme or table
p. 1437 - 1439
(2009/09/07)
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- Chemoenzymatic dynamic kinetic resolution of allylic alcohols: A highly enantioselective route to acyloin acetates
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Dynamic kinetic resolution (DKR) of a series of sterically hindered allylic alcohols has been conducted with Candida antarctica lipase B (CALB) and ruthenium catalyst 1. The optically pure allylic acetates obtained were subjected to oxidative cleavage to
- Bogar, Krisztian,Vidal, Pilar Hoyos,Alcantara Leon, Andres R.,Baeckvall, Jan-E.
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p. 3401 - 3404
(2008/02/12)
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- A new approach to the Nazarov reaction via sequential electrocyclic ring opening and ring closure
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Regioselective dichlorocyclopropanation of 2-silyloxydienes furnishes vinylcyclopropanol silyl ethers in good yield. Treatment with silver(I) at room temperature effects disrotatory electrocyclic opening to a 2-chloro-3-silyloxypentadienyl cation, which then undergoes conrotatory (Nazarov) electrocyclization to provide chlorocyclopentenones. This two-step sequence offers a convenient and mild alternative to the standard Nazarov cyclization protocol via a formal 4+1 construction and furnishes products containing useful halogen functionality. In one case possessing a pendant phenyl group, interrupted Nazarov reaction to give a benzohydrindenone was observed. Copyright
- Grant, Tina N.,West
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p. 9348 - 9349
(2007/10/03)
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- Enantioselective acylation of secondary alcohols catalyzed by chiral N-heterocyclic carbenes
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(Chemical Equation Presented). The synthetic utility of chiral N-heterocyclic carbenes, which have been used mainly in transition metal-catalyzed reactions as a ligand, was demonstrated by the enantioselective acylation of secondary alcohols.
- Kano, Taichi,Sasaki, Kouji,Maruoka, Keiji
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p. 1347 - 1349
(2007/10/03)
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- Transfer hydrogenation of activated C=C bonds catalyzed by ruthenium amido complexes: Reaction scope, limitation, and enantioselectivity
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(Chemical Equation Presented) It was found that the chemoselectivity could be completely switched from C=O to C=C bonds in the transfer hydrogenation of activated α,β-unsaturated ketones catalyzed by diamine-ruthenium complex. Moreover, this addition via metal hydride had been applied to the reduction of various activated olefins. The electron-withdrawing ability of functional groups substituted on C=C bonds at the α- or β-position had strong influence on the reactivity. In addition, a wide variety of chiral diamine-Ru(II)-(arene) systems was investigated to explore the asymmetric transfer hydrogenation of prochiral α,α-dicyanoolefins. Two parameters had been systematically studied, (i) the structure of the N-sulfonylated chiral diamine ligands, in which several chiral diamines substituted on the benzene ring of DPEN were first reported, and (ii) the structure of the metal precursors, and high enantioselectivitiy (up to 89% ee) at the β-carbon was obtained.
- Xue, Dong,Chen, Ying-Chun,Cui, Xin,Wang, Qi-Wei,Zhu, Jin,Deng, Jin-Gen
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p. 3584 - 3591
(2007/10/03)
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- The Heck-type arylation of allylic alcohols with arenediazonium salts
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The Heck coupling of ArN2BF4 with secondary allylic alcohols, carried out in methanol using Pd(dba)2 as catalyst without extra ligands and base, leads to the corresponding β-arylated carbonyl compounds. Such conditions afford arylated acetals from primary allylic alcohols.
- Masllorens, Judit,Bouquillon, Sandrine,Roglans, Anna,Hénin, Fran?oise,Muzart, Jacques
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p. 3822 - 3826
(2007/10/03)
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- Titanium fluoride complexes as catalysts for the enantioselective addition of Me3Al to aldehydes
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We report a Ti(IV) catalyst prepared in situ from TiF4 for the asymmetric addition of trimethylaluminum to aldehydes. The process we detail herein does not necessitate the use of excess trimethylaluminum or Ti(IV) reagent. Good enantioselectivities are achieved with a variety of aromatic and heteroaromatic aldehydes with the products isolated in high yield.
- Pagenkopf, Brian L.,Carreira, Erick M.
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p. 9593 - 9596
(2007/10/03)
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- The Epoxy-Ramberg-Backlund reaction: A new route to allylic alcohols
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A new variant of the Ramberg-Backlund reaction is described, the epoxy-Ramberg-Backlund reaction (ERBR), in which α,β-epoxysulfones, on treatment with base, are converted into a range of mono-, di- and tri-substituted allylic alcohols. The scope and limitations of the ERBR are discussed.
- Evans, Paul,Taylor, Richard J. K.
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p. 3055 - 3058
(2007/10/03)
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