- Enantioselective epoxidation of β,β-disubstituted enamides with a manganese catalyst and aqueous hydrogen peroxide
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Enantioselective epoxidation of β,β-disubstituted enamides with aqueous hydrogen peroxide and a novel manganese catalyst is described. Epoxidation is stereospecific and proceeds fast under mild conditions. Amides are disclosed as key functional groups to enable high enantioselectivity.
- Clarasó, Carlota,Vicens, Laia,Polo, Alfonso,Costas, Miquel
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supporting information
p. 2430 - 2435
(2019/03/29)
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- Rh-Catalyzed Asymmetric Hydrogenation of β-Branched Enol Esters for the Synthesis of β-Chiral Primary Alcohols
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An asymmetric hydrogenation of β-branched enol esters has been developed for the first time, providing a new route for the synthesis of β-chiral primary alcohols. Using a (S)-SKP-Rh complex bearing a large bite angle and enol ester substrates possessing an O-fomyl directing group, the desired products were obtained in quantitative yields and with excellent enantioselectivities.
- Liu, Chong,Yuan, Jing,Zhang, Jian,Wang, Zhihui,Zhang, Zhenfeng,Zhang, Wanbin
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supporting information
p. 108 - 111
(2018/01/17)
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- The synthesis of non-racemic β-alkyl-β-aryl-disubstituted allyl alcohols and their transformation into allylamines and amino acids bearing a quaternary stereocenter
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A synthesis of non-racemic β-alkyl-β-aryl allyl alcohols and their transformation into allylamines bearing a quaternary stereogenic center is reported. The allyl alcohols were prepared either by Cu-catalyzed enantioselective reduction of enones or by sequ
- Narczyk, Aleksandra,Pieczykolan, Micha?,Stecko, Sebastian
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supporting information
p. 3921 - 3946
(2018/06/08)
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- Enantioselective Hydrogenation of β,β-Disubstituted Unsaturated Carboxylic Acids under Base-Free Conditions
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An additive-free enantioselective hydrogenation of β,β-disubstituted unsaturated carboxylic acids catalyzed by the Rh-(R,R)-f-spiroPhos complex has been developed. Under mild conditions, a wide scope of β,β-disubstituted unsaturated carboxylic acids were hydrogenated to the corresponding chiral carboxylic acids with excellent enantioselectivities (up to 99.3% ee). This methodology was also successfully applied to the synthesis of the pharmaceutical molecule indatraline.
- Yan, Qiaozhi,Kong, Duanyang,Zhao, Wei,Zi, Guofu,Hou, Guohua
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p. 2070 - 2077
(2016/03/15)
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- Ruthenium-catalyzed oxidation of allyl alcohols with intermolecular hydrogen transfer: Synthesis of α,β-unsaturated carbonyl compounds
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Ruthenium-catalyzed oxidation of multisubstituted allyl alcohols in the presence of benzaldehyde gives enals or enones in good yields. Unlike the commonly reported ruthenium-catalyzed isomerization reaction of allyl alcohols to give saturated ketones, an intermolecular rather than intramolecular hydrogen transfer is involved in this transformation. This reaction offers an efficient, mild, and high-yielding method for the preparation of substituted α,β-unsaturated compounds.
- Ren, Kai,Hu, Bei,Zhao, Mengmeng,Tu, Yahui,Xie, Xiaomin,Zhang, Zhaoguo
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p. 2170 - 2177
(2014/04/03)
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- Enantioselective halogenative semi-pinacol rearrangement: A stereodivergent reaction on a racemic mixture
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An efficient, quantitative deracemization strategy for optically inactive allylic cycloalkanols has been achieved using the biphasic halogenative semi-pinacol reaction protocol. The resultant β-halo spiroketones, containing three contiguous stereogenic ce
- Romanov-Michailidis, Fedor,Pupier, Marion,Gune, Laure,Alexakis, Alexandre
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supporting information
p. 13461 - 13464
(2015/02/19)
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- Highly enantioselective asymmetric hydrogenation of (E)-β,β- disubstituted α,β-unsaturated Weinreb amides catalyzed by Ir(i) complexes of SpinPhox ligands
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The Ir(i) complexes of chiral spiro phosphino-oxazoline ligands (SpinPhox) have demonstrated good to excellent enantioselectivity in the asymmetric hydrogenation (AH) of a variety of (E)-β,β-disubstituted α,β-unsaturated N-methoxy-N-methylamides, affording the corresponding optically active Weinreb amides with up to 97% ee.
- Shang, Jian,Han, Zhaobin,Li, Yang,Wang, Zheng,Ding, Kuiling
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supporting information; experimental part
p. 5172 - 5174
(2012/06/18)
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- Highly enantioselective iridium-catalyzed hydrogenation of α,β-unsaturated esters
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α,β-Unsaturated esters have been employed as substrates in iridium-catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic- and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. Asymmetric hydrogenation: A variety of α,β-unsaturated esters were hydrogenated with high enantioselectivities (see scheme). The hydrogenated products have been used in synthetic transformations as well as in formal total syntheses. Copyright
- Li, Jia-Qi,Quan, Xu,Andersson, Pher G.
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supporting information
p. 10609 - 10616
(2012/11/07)
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- Highly enantioselective asymmetric isomerization of primary allylic alcohols with an iridium-N,P complex
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Access to chiral aldehydes: The asymmetric isomerization of primary allylic alcohols was studied with a bicyclic phosphine-oxazoline iridium catalyst. This method displays a broad substrate scope and leads to the desired chiral aldehydes with excellent enantioselectivities (see scheme; R1, R 2=Ar or alkyl). Copyright
- Li, Jia-Qi,Peters, Byron,Andersson, Pher G.
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supporting information; experimental part
p. 11143 - 11145
(2011/10/31)
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- Pd-catalyzed asymmetric hydrogenation of C=C bond of α,β- unsaturated ketones
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Homogenous palladium-catalyzed asymmetric hydrogenation of C=C double bond of ,-unsaturated ketones has been -developed by using palladium(II) trifluoroacetate/(S)-7,7-bis-[di(4-methoxyphenyl]phosphino)-1,1-spirobiindane complex [Pd(OCOCF3)2-(S)-An-SDP] as the catalyst under ambient hydrogen pressure and room temperature with up to 89% ee. Georg Thieme Verlag Stuttgart · New York.
- Wang, Duo-Sheng,Wang, Da-Wei,Zhou, Yong-Gui
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supporting information; experimental part
p. 947 - 950
(2011/06/17)
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- Improved catalysts for the iridium-catalyzed asymmetric isomerization of primary allylic alcohols based on charton analysis
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An improved generation of chiral cationic iridium catalysts for the asymmetric isomerization of primary allylic alcohols is disclosed. The design of these air-stable complexes relied on the preliminary mechanistic information available, and on Charton analyses using two preceding generations of iridium catalysts developed for this highly challenging transformation. Sterically unbiased chiral aldehydes that were not accessible previously have been obtained with high levels of enantioselectivity, thus validating the initial hypothesis regarding the selected ligand-design elements. A rationale for the high enantioselectivities achieved in most cases is also presented. Achieving enantioselectivity: An improved generation of chiral cationic iridium catalysts for the asymmetric isomerization of primary allylic alcohols is disclosed. The design of these air-stable complexes relies on preliminary mechanistic information and on Charton analyses using two preceding generations of iridium catalysts developed for this highly challenging transformation (see figure).
- Mantilli, Luca,Gerard, David,Torche, Sonya,Besnard, Celine,Mazet, Clement
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supporting information; experimental part
p. 12736 - 12745
(2011/02/21)
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- Iridium-catalyzed asymmetric isomerization of primary allylic alcohols
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Nothing to sm(Ir)k at: Under appropriate reaction conditions, iridium hydride catalysts promote the isomerization of primary allylic alcohols. The best catalysts, like (R)-1 (P green, O red, N blue, Ir yellow), deliver the desired chiral aldehydes with excellent enantioselectivity and good yields. Mechanistic hypotheses have been developed on the basis of preliminary investigations.
- Mantilli, Luca,Gerard, David,Torche, Sonya,Besnard, Celine,Mazet, Clement
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supporting information; experimental part
p. 5143 - 5147
(2009/12/07)
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- Highly chemo- And enantioselective hydrogenation of linear α,β-unsaturated ketones
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A study was conducted to report the synthesis of sulfoximine-derived P,N-ligands and their applications in indium-catalyzed asymmetric hydrogenation reactions. Investigations were conducted using linear β,β- disubstituted 1,3-diphenyl-2-butenone as model substrate and iridium, having a ketonic phenyl group and two alkyl substituents at the olefinic β-positions. Methyl ketone with β-methyl and β-phenyl substituent was also applied in the investigations.
- Lu, Sheng-Mei,Bolm, Carsten
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supporting information; experimental part
p. 7513 - 7516
(2009/09/06)
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- A new entry to Pd-H chemistry: Catalytic asymmetric conjugate reduction of enones with EtOH and a highly enantioselective synthesis of warfarin
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(Chemical Equation Presented) We report here the catalytic asymmetric conjugate reduction of enones using ethanol as a hydride source. The reaction was carried out in the presence of a chiral Pd complex at ambient temperature in ethanol, and the desired products were obtained in high chemical yield and high enantioselectivity. We applied this novel reaction to the catalytic asymmetric synthesis of warfarin (96% ee), and on the basis of d-labeling experiments, the reaction mechanism is proposed.
- Tsuchiya, Yasunori,Hamashima, Yoshitaka,Sodeoka, Mikiko
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p. 4851 - 4854
(2007/10/03)
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- Asymmetric conjugate reduction of α,β-unsaturated ketones and esters with chiral rhodium(2,6-bisoxazolinylphenyl) catalysts
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New asymmetric conjugate reduction of β,β-disubstituted α,β-unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6-bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)-4-Phenyl-3-penten-2- one and (E)-4-phenyl-4-isopropyl-3-penten-2-one were readily reduced at 60°C in 95% ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO) 2MeSiH proved to be the best hydrogen donor of choice. tert-Butyl (E)-β-methylcinnamate and β-isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98% ee.
- Kanazawa, Yoshinori,Tsuchiya, Yasunori,Kobayashi, Kazuki,Shiomi, Takushi,Itoh, Jun-Ichi,Kikuchi, Makoto,Yamamoto, Yoshihiko,Nishiyama, Hisao
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- Synthesis of isoaminile mediated by enzymes
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A lipase-mediated synthesis of all four enantiomers of isoaminile is reported. The key issues of the paper are: (i) enantioselective acetylation of allylic alcohol (E)-(±)-5 to give (E,S)-5 (ee = 92%) and (E,R)-6 (ee > 99%); (ii) Claisen-Johnson rearrange
- Antonietti, Fabrizio,Brenna, Elisabetta,Fuganti, Claudio,Gatti, Francesco G.,Giovenzana, Tommaso,Grande, Valentina,Malpezzi, Luciana
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p. 1148 - 1156
(2007/10/03)
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- Pd-catalyzed addition of organoboronic acids to alkynes at room temperature
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Combination of Pd(OAc)2 with 2-bromo-1,3-bis- [diphenylphosphenomethyl)]benzene (1) or 2-bromo-1,3-bis-[di-tert- butylphosphenomethyl)]benzene (3) catalyzed hydroarylations and hydroalkenylations of various alkynes more efficiently in terms of
- Gupta, Arun Kumar,Kim, Ki Seong,Oh, Chang Ho
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p. 457 - 460
(2007/10/03)
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- Palladium-catalyzed cascade reaction of α,β-unsaturated sulfones with aryl iodides
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Unlike traditionally used acyclic 1,2-disubstituted alkenes, the reaction of α,β-unsaturated phenyl sulfones with aryl iodides under Heck reaction conditions (Pd(OAc)2 as catalyst, Ag2-CO3 as base in DMF at 120°C) takes place mainly by a cascade process, involving one unit of the alkene and three units of the aryl iodide, to afford a substituted 9-phenylsulfonyl-9,10-dihydrophenanthrene, The dominant formation of this 3:1 coupling product, instead of the Heck trisubstituted olefin, shows that aromatic C-H activation processes can compete with the usually fast syn β-hydrogen elimination step in the Heck arylation of an acyclic olefin. The structural scope of this palladium-catalyzed cascade arylation of α,β-unsaturated sulfones has proved to be wide with regard to substitution at the β-position (alkyl, aryl, or alkenyl substitution), substitution at the sulfone unit (alkyl or phenyl sulfones), and configuration at the C=C bond (trans or cis). Moreover, although less favored than in the case of the arylation of α,β-unsaturated sulfones, similarly substituted 9,10-dihydrophenanthrenes have also been obtained in the case of α,β-unsaturated phosphine oxides and α,β-unsaturated phosphonate esters. A Pd0-pdII-pdIV mechanistic pathway involving the successive formation of highly electrophilic σ-alkylpalladium intermediates and palladacycles is proposed for this multi-component arylation.
- Mauleon, Pablo,Nunez, Angel A.,Alonso, Ines,Carretero, Juan C.
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p. 1511 - 1520
(2007/10/03)
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- A versatile new catalyst for the enantioselective isomerization of allylic alcohols to aldehydes: Scope and mechanistic studies
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A new planar-chiral bidentate phosphaferrocene ligand (2) has been synthesized and structurally characterized. The derived rhodium complex, [Rh(cod)(2)]BF4, serves as an effective catalyst for asymmetric isomerizations of allylic alcohols to aldehydes, furnishing improved yields, scope, and enantioselectivities relative to previously reported methods. The catalyst is air-stable and can be recovered at the end of the reaction. Mechanistic studies establish that the isomerization proceeds via an intramolecular 1,3-hydrogen migration and that the catalyst differentiates between the enantiotopic C1 hydrogens.
- Tanaka, Ken,Fu, Gregory C.
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p. 8177 - 8186
(2007/10/03)
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- Stereochemistry of the Reactions of CuI Catalyzed Grignard Reagents with Ethyl (E)- and (Z)-β-Chlorocinnamates
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Ethyl (E)- and (Z)-3-chloro-3-phenyl-2-propenoate were prepared and separated.The (Z)-isomer gave β-alkylated ethyl cinnamates in good yield when reacted with alkyl Grignard reagents in the presence of 10percent CuI.The (Z)-isomer reacted with retention o
- Jalander, Lars,Broms, Merete
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p. 173 - 178
(2007/10/02)
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- Stereochemistry of the Reaction of Diorganocuprate(I) Complexes Derived from Grignard Reagents with α,β-Acetylenic Esters
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Diorganocuprate(I) complexes RCH3CuMgX, prepared from methylcopper and Grignard reagents (i-PrMgBr and t-BuMgCl) gave mainly cis-1,4-addition of the alkyl group originally present in the Grignard reagents and small amounts of cis- and trans-1,4-addition of the methyl group introduced by methylcopper, when they were allowed to react with ethyl propiolate and ethyl phenylpropiolate.The proportion of cis-1,4-addition products did not change when the reaction temperature was raised from -78 deg C to room temperature.The configurations of the main reaction products from the reaction with ethyl phenylpropiolate, ethyl (Z)-β-isopropylcinnamate and ethyl (Z)-β-t-butylcinnamate, were established by conversion of the corresponding acids to β-isopropylindenone and β-t-butylindenone.
- Jalander, Lars,Iambolieva, Kostadinka,Sundstroem, Viola
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p. 715 - 720
(2007/10/02)
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