- Computational Insight into 1,2-Diamine, -Diether, and -Amino Ether Chiral Ligand-Mediated Carbolithiation: A Case of Enantioinduction Reversal
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trans-1,2-Cyclohexanediamine, -diether, and -amino ether were compared as chiral inducers in the asymmetric intramolecular carbolithiation of olefinic aryllithiums. Switching from diamine to ethereal ligands inverts the sense of asymmetric induction. This reversal of stereoselectivity was investigated through density functional theory calculations. High enantioselectivities observed with diether and amino ether ligands arise from favorable weak interactions between the ligand and the substrate. The relative efficiency of the three ligands and sense of stereoinduction for the most efficient diether and amino ether ligands prove to be foreseeable by modeling the reaction with the parent achiral 1,2-bidentate additives and comparing the diastereomeric transition states stemming from the two half-chair conformations of their lithium chelate.
- Guyon, Hélène,Castanet, Anne-Sophie,Boussonnière, Anne
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p. 8933 - 8943
(2020/08/28)
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- Readily Accessible 1,2-Amino Ether Ligands for Enantioselective Intramolecular Carbolithiation
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A new class of chiral 1,2-amino ether ligands, readily accessible from naturally occurring α-amino- or α-hydroxy acids, was found to provide high levels of both conversion and stereocontrol (up to 95:5 er) in intramolecular carbolithiation reactions, outperforming the benchmark ligand (?)-sparteine. The ligand could be used in a substoichiometric amount (0.25 equiv) without significant loss of enantioselectivity.
- Guyon, Hélène,Boussonnière, Anne,Castanet, Anne-Sophie
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p. 4949 - 4957
(2017/05/12)
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- A New Generation of Smart Amine Donors for Transaminase-Mediated Biotransformations
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The application of ω-transaminase biocatalysts for the synthesis of optically pure chiral amines presents a number of challenges, including difficulties associated with displacing the challenging reaction equilibria. Herein, we report a highly effective approach using low equivalents of the new diamine donor, cadaverine, which enables high conversions of challenging substrates to the corresponding chiral amines in excellent ee. This approach paves the way for the design of self-sufficient fermentation processes combining transaminase biotransformations with existing strategies for cadaverine production by decarboxylation of endogenous lysine.
- Gomm, Andrew,Lewis, William,Green, Anthony P.,O'Reilly, Elaine
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supporting information
p. 12692 - 12695
(2016/08/30)
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- Enantioselective Synthesis of Carbo- and Heterocycles through a CuH-Catalyzed Hydroalkylation Approach
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The enantioselective, intramolecular hydroalkylation of halide-tethered styrenes has been achieved through a copper hydride-catalyzed process. This approach allowed for the synthesis of enantioenriched cyclobutanes, cyclopentanes, indanes, and six-membered N- and O-heterocycles. This protocol was applied to the synthesis of the commercial serotonin reuptake inhibitor (ˉ)-paroxetine.
- Wang, Yi-Ming,Bruno, Nicholas C.,Placeres, ángel L.,Zhu, Shaolin,Buchwald, Stephen L.
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supporting information
p. 10524 - 10527
(2015/09/28)
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- ENANTIOPURE BASE-METAL CATALYSTS FOR ASYMMETRIC CATALYSIS AND BIS(IMINO)PYRIDINE IRON ALKYL COMPLEXES FOR CATALYSIS
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Disclosed herein are iron, nickel, or cobalt compounds having tridentate ligands, which can have at least one chiral moiety in the molecular structure thereof and the use of these compounds for the hydrogenation and transformation of olefins (preferably prochiral) and alkynes.
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Paragraph 0145; 0146; 0147
(2013/04/10)
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- Enantiopure C1-symmetric bis(imino)pyridine cobalt complexes for asymmetric alkene hydrogenation
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Enantiopure C1-symmetric bis(imino)pyridine cobalt chloride, methyl, hydride, and cyclometalated complexes have been synthesized and characterized. These complexes are active as catalysts for the enantioselective hydrogenation of geminal-disubstituted olefins.
- Monfette, Sebastien,Turner, Zoe R.,Semproni, Scott P.,Chirik, Paul J.
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supporting information; experimental part
p. 4561 - 4564
(2012/04/23)
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- Iridium-catalyzed asymmetric hydrogenation of olefins using TIQ phosphine-oxazoline ligands
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A novel family of tetrahydroisoquinoline (TIQ) phosphine-oxazoline ligands and four corresponding iridium complexes have been developed and applied to the asymmetric hydrogenation of unfunctionalized olefins. The results showed that the best conversion rates were observed in up to 99% with an enantiomeric excess of 91%.
- Chakka, Sai Kumar,Peters, Byron K.,Andersson, Pher G.,Maguire, Glenn E.M.,Kruger, Hendrik G.,Govender, Thavendran
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experimental part
p. 2295 - 2301
(2010/11/04)
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- BINAP-Ru(II) and BINAP-Rh(I)-catalyzed asymmetric hydrogenation of olefins without heteroatom-functionalities
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Asymmetric hydrogebation of 1,1'-disubstituted olefins which have no heteroatom functionalities to allow additional interactions with catalyst centers, have been investigated by use of Ru(II) and Rh(I) complexes of BINAP as catalysts.Enantioselectivities and the sense of asymmetric induction are highly dependent on the structure of substrates and the nature of catalysts.Hydrogenation of 1-methyleneindan (1a), a five-membered methylenecycloalkane, gave the highest optical yield (78percent) when Ru(OAc)2((R)-binap) was used as catalyst, while the use of the catalyst system 2/(R)-BINAP afforded the highest ees (71-82percent) for six-membered analogs, 1-methylenetetralin (4a) and its derivatives.In ciontrast, hydrogenation of seven-membered analog 7 and acyclic olefins 10 resulted in only moderate enantioselectivities by use of these catalysts.The BINAP-Ru(II) catalyzed hydrogenation exhibited a remarkable dependence of enantioselectivities on solvents, while a large anionic ligand effect was observed for the reaction with the BINAP-Rh(I) system.Based on these experimental results, mechanistic aspects of these asymmetric hydrogenation have been discussed.Keywords: Ruthenium; Rhodium; BINAP; Assymetric hydrogenation; Simple olefins; Catalysis
- Ohta, Tetsuo,Ikegami, Hiroshi,Miyake, Tsutomu,Takaya, Hidemasa
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p. 169 - 176
(2007/10/02)
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- On the Absolute Configuration of (+)-Indane-1-carboxylic Acid
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The (R)-configuration, attributed to (+)-indane-carboxylic acid ((+)-1) by Fredga, is unequivocally confirmed (Scheme 1).Configurational doubts, raised by an erroneous ORD. curve of (-)-1-methylindane ((-)-4) published by Brewster and Buta, are unfounded (cf. the following paper of Brewster and the corrections in ).This was further verified by preparing deuteriated 1-methylindanes starting with (-)-(R)-3-phenylbutyric acid ((-)-(R)-5) as well as with (+)-(R)-1 or (-)-(S)-1 (Scheme 2).The ORD. curves of the optically active 4 thus obtained were (disregarding deuterium isotope effects) identical or antipodal, respectively (cf.Fig.1,2, and 7a-e).Optically active methyl indane-1-carboxylates ((-)-(R)-14 or (+)-(S)--14) show a strong solvent dependence of their ORD. and CD. spectra with a sign inversion occuring in going from isooctane to methanol or benzene.The observed changes can be explained by a change in the population of comformations where the ester carbonyl group is eclipsed either with the C(1),C(2)- or C(1),H-bond, with the n,?*-transition having a slightly different energy and the ester group an essentially enantiomeric environment with respect to its orientation relative to the benzene moiety.
- Hansen, Hans-Juergen,Sliwka, Hans-Richard,Hug, Werner
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p. 325 - 343
(2007/10/02)
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- Absorption Spectra and Photochemical Rearrangements in Phenylalkene Cations in Solid Argon
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Matrix photoionization experiments with phenylalkenes produced and trapped the parent molecular cations in solid argon at 20 K.In the substituted styrene cation cases, structure was resolved in red and ultraviolet absorption bands and assigned to Ph-C stretching and Ph-C=C bending modes.Molecular ion rearrangements were observed during sample formation and upon the photolysis of the cold sample; allylbenzene cation rearranged to β-methylstyrene cation and indan cation with 290 nm irradiation.The matrix absorption bands were substantially sharper than photodissociati on spectra, which suggests that excess internal energy may contribute substantially to the bandwidth of gaseous molecular ions produced by electron impact.
- Andrews, Lester,Harvey, James A.,Kelsall, Benuel J.,Duffey, Donald C.
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p. 6415 - 6422
(2007/10/02)
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