- Chiral Ugi-type amines: Practical synthesis, ligand development, and asymmetric catalysis
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Ugi's amine has become one type of privileged chiral skeleton for chiral ligand design bearing central/planar chirality, and such ligands have exhibited tremendous success in various asymmetric catalysis. However, the current access to enantiopure Ugi's amine is quite tedious and relies heavily on optical resolution, which impedes its practical applications, to some extent. Herein, we present a facile asymmetric synthesis of enantioenriched Ugi-type amines bearing a long-carbon chain through Ir-catalyzed cascade allylation/2-aza-Cope rearrangement, followed by amino exchange and Pd/C-catalyzed one-pot hydrogenation/reductive amination. The protocol could be readily scaled up, and it has been conducted in 20-g-scale asymmetric synthesis of (S)-Ugi-type amine from commercially available reagents, in >99% ee and >70% overall yield in four steps with one short silica gel-plug purification. (S,Rp)-PPFA-type and (S,Rp)-Josiphos-type ligands, readily prepared from the achieved Ugi-type amine, exhibited higher or comparable asymmetric induction and catalytic efficacy in several Cu(I)-catalyzed asymmetric reactions, which indicated great potential of the applications of the readily accessible Ugi-type amines in ligand/catalyst design.
- Wang, Chun-Jiang,Dong, Wu-Wei,Li, Yi-Nan,Chang, Xin,Shen, Chong
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- Iron-Catalyzed Tunable and Site-Selective Olefin Transposition
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The catalytic isomerization of C-C double bonds is an indispensable chemical transformation used to deliver higher-value analogues and has important utility in the chemical industry. Notwithstanding the advances reported in this field, there is compelling demand for a general catalytic solution that enables precise control of the C═C bond migration position, in both cyclic and acyclic systems, to furnish disubstituted and trisubstituted alkenes. Here, we show that catalytic amounts of an appropriate earth-abundant iron-based complex, a base and a boryl compound, promote efficient and controllable alkene transposition. Mechanistic investigations reveal that these processes likely involve in situ formation of an iron-hydride species which promotes olefin isomerization through sequential olefin insertion/β-hydride elimination. Through this strategy, regiodivergent access to different products from one substrate can be facilitated, isomeric olefin mixtures commonly found in petroleum-derived feedstock can be transformed to a single alkene product, and unsaturated moieties embedded within linear and heterocyclic biologically active entities can be obtained.
- Yu, Xiaolong,Zhao, Haonan,Li, Ping,Koh, Ming Joo
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supporting information
p. 18223 - 18230
(2020/12/04)
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- Chiral auxiliary recycling in continuous flow: Automated recovery and reuse of Oppolzer's sultam
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The telescoping of a three-stage, chiral auxiliary-mediated transformation in flow is described, including continuous separation of the product and auxiliary. The auxiliary can either be collected for later reuse, or directly fed back to the beginning of the process for recycling in real time, enabling each molecule of auxiliary to make multiple equivalents of chiral product and thus minimizing the step- and atom-economy issues associated with auxiliary-mediated synthesis. This concept is demonstrated for the asymmetric hydrogenation of olefins using Oppolzer's sultam, shortening the total reaction time >100 fold compared to batch, and demonstrating formal sub-stoichiometric auxiliary loading with respect to the process by automating auxiliary recycling within a closed loop.
- Sullivan,Newman
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p. 2130 - 2134
(2018/03/05)
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- Asymmetric NaBH4 1,4-reduction of C3-disubstituted 2-propenoates catalyzed by a diamidine cobalt complex
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A new Co complex of a unique diamidine ligand catalyzes asymmetric NaBH4 reduction of C3-disubstituted (E)- and (Z)-2-propenoates, including C3-oxygen- and nitrogen-substituted substrates with high enantioselectivity. Analysis by X-ray diffract
- Shuto, Yoshihiro,Yamamura, Tomoya,Tanaka, Shinji,Yoshimura, Masahiro,Kitamura, Masato
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p. 1547 - 1550
(2015/05/27)
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- Enantioselective conjugate addition of alkylboranes catalyzed by a copper- N-heterocyclic carbene complex
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The first catalytic enantioselective conjugate addition of alkylboron compounds has been achieved. Reactions between alkylboranes and imidazol-2-yl α,β-unsaturated ketones proceeded with high enantioselectivity under the influence of a Cu(I) catalyst syst
- Yoshida, Mika,Ohmiya, Hirohisa,Sawamura, Masaya
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supporting information; experimental part
p. 11896 - 11899
(2012/09/07)
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- Highly efficient copper(I) iodide-tolyl-BINAP-catalyzed asymmetric conjugate addition of methylmagnesium bromide to α,β-unsaturated esters
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A highly efficient asymmetric conjugate addition of methylmagnesium bromide (MeMgBr) to α,β-unsaturated esters catalyzed by copper(I) iodide-tolyl-BNIP (CuI-Tol-BINAP) is described.
- Wang, Shun-Yi,Lum, Tze-Keong,Ji, Shun-Jun,Loh, Teck-Peng
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supporting information; experimental part
p. 673 - 677
(2009/04/10)
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- Copper-catalyzed enantioselective conjugate addition of Grignard reagents to α,β-unsaturated esters
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(Chemical Equation Presented) Stable dinuclear Cu complexes have been used to catalyze the conjugate addition of inexpensive and readily available Grignard reagents to acyclic α,β-unsaturated esters. The method provides the correspending β-substituted optically active esters in high yields and with excellent enantioselectivities (see scheme). R3 = cyclohexyl, R 4 = Ph or R3 = Ph, R4 = cyclohexyl.
- Lopez, Fernando,Harutyunyan, Syuzanna R.,Meetsma, Auke,Minnaard, Adriaan J.,Feringa, Ben L.
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p. 2752 - 2756
(2007/10/03)
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- Asymmetric Conjugate Addition of Organometallic Reagents to Chiral Vinyl Sulfoximines
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The chiral vinyl sulfoximines 1 and 2 (R' = C6H5, CH3, n-Bu, C6H5CH2CH2) have been prepared; they undergo conjugate addition reactions with organometallic reagents with high asymmetric induction.These conjugate addition adducts have been converted to chiral 3-alkylalkanoic acids in high enantiomeric excess (>90percent)
- Pyne, Stephen G.
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