- Merging Halogen-Atom Transfer (XAT) and Cobalt Catalysis to Override E2-Selectivity in the Elimination of Alkyl Halides: A Mild Route towardcontra-Thermodynamic Olefins
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We report here a mechanistically distinct tactic to carry E2-type eliminations on alkyl halides. This strategy exploits the interplay of α-aminoalkyl radical-mediated halogen-atom transfer (XAT) with desaturative cobalt catalysis. The methodology is high-yielding, tolerates many functionalities, and was used to access industrially relevant materials. In contrast to thermal E2 eliminations where unsymmetrical substrates give regioisomeric mixtures, this approach enables, by fine-tuning of the electronic and steric properties of the cobalt catalyst, to obtain high olefin positional selectivity. This unprecedented mechanistic feature has allowed access tocontra-thermodynamic olefins, elusive by E2 eliminations.
- Zhao, Huaibo,McMillan, Alastair J.,Constantin, Timothée,Mykura, Rory C.,Juliá, Fabio,Leonori, Daniele
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supporting information
p. 14806 - 14813
(2021/09/18)
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- Manganese-Catalyzed Desaturation of N-Acyl Amines and Ethers
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Enamines and enol ethers are versatile synthons for chemical synthesis. While several methods have been developed to access such molecules, prefunctionalized starting materials are usually required, and direct desaturation methods remain rare. Herein, we report direct desaturation reactions of N-protected cyclic amines and cyclic ethers using a mild I(III) oxidant, PhI(OAc)2, and an electron-deficient manganese pentafluorophenylporphyrin catalyst, Mn(TPFPP)Cl. This system displays high efficiency for α,β-desaturation of various cyclic amines and ethers. Mechanistic probes suggest that the desaturation reaction occurs via an initial α-C-H hydroxylation pathway, which serves to protect the product from overoxidation.
- Li, Gang,Kates, Patrick A.,Dilger, Andrew K.,Cheng, Peter T.,Ewing, William R.,Groves, John T.
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p. 9513 - 9517
(2019/10/14)
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- Enantioselective Pd-catalyzed α-arylation of N-Boc-pyrrolidine: The key to an efficient and practical synthesis of a glucokinase activator
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(Chemical Equation Presented) A short and practical synthesis of glucokinase activator 1 was achieved utilizing a convergent strategy involving SNAr coupling of activated aryl fluoride 11 with hydroxypyridine 9. The key to the success of the synthesis was the development of a novel method for enantioselective formation of α-arylpyrrolidines during the course of the project. In this method, (-)-sparteine-mediated enantioselective lithiation of N-Boc-pyrrolidine was followed by in situ transmetalation to zinc and Pd-catalyzed coupling with aryl bromide 3, proceeding in 92% ee. This transformation allowed the preparation of compound 1 in a 31% overall yield over six steps.
- Klapars, Artis,Campos, Kevin R.,Waldman, Jacob H.,Zewge, Daniel,Dormer, Peter G.,Chen, Cheng-Yi
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p. 4986 - 4993
(2008/12/21)
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