- Palladium-catalyzed C-H activation of N-Allyl Imines: Regioselective allylic alkylations to deliver substituted aza-1,3-dienes
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A new mode of activation of an imine via a rare aza-substituted π-allyl complex is described. Palladium-catalyzed C(sp3)-H activation of the N-allyl imine and the subsequent nucleophilic attack by the α-alkyl cyanoester produced the 1-aza-1,3-d
- Trost, Barry M.,Mahapatra, Subham,Hansen, Martin
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- Kinetic and Dynamic Kinetic Resolution of Racemic Tertiary Bromides by Pentanidium-Catalyzed Phase-Transfer Azidation
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We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium-catalyzed kinetic resolution (KR) of racemic tertiary bromides under base-free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a SN2X pathway.
- Ban, Xu,Lee, Richmond,Ren, Jingyun,Tan, Choon-Hong,Tan, Siu Min,Zhang, Xin
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supporting information
p. 9055 - 9058
(2020/03/30)
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- Enantioselective construction of tetrasubstituted stereogenic carbons through bronsted base catalyzed michael reactions: α′-hydroxy enones as key enoate equivalent
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Catalytic and asymmetric Michael reactions constitute very powerful tools for the construction of new C-C bonds in synthesis, but most of the reports claiming high selectivity are limited to some specific combinations of nucleophile/electrophile compound types, and only few successful methods deal with the generation of all-carbon quaternary stereocenters. A contribution to solve this gap is presented here based on chiral bifunctional Bronsted base (BB) catalysis and the use of α′-oxy enones as enabling Michael acceptors with ambivalent H-bond acceptor/donor character, a yet unreported design element for bidentate enoate equivalents. It is found that the Michael addition of a range of enolizable carbonyl compounds that have previously demonstrated challenging (i.e., α-substituted 2-oxindoles, cyanoesters, oxazolones, thiazolones, and azlactones) to α′-oxy enones can afford the corresponding tetrasubstituted carbon stereocenters in high diastereo- and enantioselectivity in the presence of standard BB catalysts. Experiments show that the α′-oxy ketone moiety plays a key role in the above realizations, as parallel reactions under identical conditions but using the parent α,β-unsaturated ketones or esters instead proceed sluggish and/or with poor stereoselectivity. A series of trivial chemical manipulations of the ketol moiety in adducts can produce the corresponding carboxy, aldehyde, and ketone compounds under very mild conditions, giving access to a variety of enantioenriched densely functionalized building blocks containing a fully substituted carbon stereocenter. A computational investigation to rationalize the mode of substrate activation and the reaction stereochemistry is also provided, and the proposed models are compared with related systems in the literature.
- Badiola, Eider,Fiser, Bla,Gmez-Bengoa, Enrique,Mielgo, Antonia,Olaizola, Iurre,Urruzuno, Iaki,Garca, Jess M.,Odriozola, Jos M.,Razkin, Jess,Oiarbide, Mikel,Palomo, Claudio
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supporting information
p. 17869 - 17881
(2015/02/19)
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- Mechanistic consideration of asymmetric CN and CC bond formations with bifunctional chiral ir and ru catalysts
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The mechanism of two enantioselective reactions, direct amination of α-cyanoacetates 3 with azodicarboxylates 4 and CC bond formation reaction of α-cyanoacetates with acetylenic esters 6, catalyzed by chiral bifunctional Ir and Ru complexes, Cp*Ir[(S,S)-N
- Hasegawa, Yasuharu,Gridnev, Ilya D.,Ikariya, Takao
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supporting information; experimental part
p. 316 - 334
(2012/05/07)
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- A highly enantio- and diastereoselective molybdenum-catalyzed asymmetric allylic alkylation of cyanoesters
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An efficient molybdenum-catalyzed asymmetric allylic alkylation (Mo-AAA) of cyanoester nucleophiles is reported. A number of highly functionalized branched cyanoesters containing a quaternary carbon stereocenter with a vicinal tertiary stereocenter are obtained. This method generates a number of functionalized cyanoesters in excellent yield and chemoselectivity in good to excellent diastereoselectivity and enantioselectivity.
- Trost, Barry M.,Miller, John R.,Hoffman Jr., Christopher M.
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supporting information; experimental part
p. 8165 - 8167
(2011/07/08)
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- Enantioselective bimetallic catalysis of michael additions forming quaternary stereocenters
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Robotlike: Low catalyst loadings of a planar-chiral ferrocenyl bispalladacycle are sufficient to catalyze the Michael addition of trisubstituted α-cyanoacetates to enones with excellent yields (TONs up to 2450) and high enantioselectivity. The reaction proceeds by a cooperative bimetallic mechanism and is superior to previous methods relying on soft Lewis acid catalysts. (Chemical Equation Presented)
- Jautze, Sascha,Peters, Rene
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supporting information; experimental part
p. 9284 - 9288
(2009/05/15)
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- Enantioselective direct amination of α-cyanoacetates catalyzed by bifunctional chiral Ru and Ir amido complexes
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The bifunctional chiral amido Ir complex catalyzed asymmetric electrophilic direct amination of α-substituted α-cyanoacetates using azodicarboxylates proceeds rapidly to provide the corresponding hydrazine adducts in high yields and with excellent ee values. Copyright
- Hasegawa, Yasuharu,Watanabe, Masahito,Gridnev, Ilya D.,Ikariya, Takao
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p. 2158 - 2159
(2008/09/18)
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