Strong Brønsted acid promoted asymmetric hydrogenation of isoquinolines and quinolines catalyzed by a Rh–thiourea chiral phosphine complex via anion binding

Wen, Jialin; Tan, Renchang; Liu, Shaodong; Zhao, Qingyang; Zhang, Xumu

doi:10.1039/c5sc04712a

Cited by 144 publications

(65 citation statements)

References 34 publications

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“…Transition metal-mediated hydrogenation 1,2 using Fe, 3 Co, 4 Ni, 5 Pd, 6,7 Pt, 8 Rh, 9,10 Ir, 11 Ru 12 or Mo 13 is a well-established procedure in research and industrial applications. However, this approach usually requires high hydrogen pressure, resulting in over reduction or functional group intolerance of the substrate.…”

Section: Introductionmentioning

confidence: 99%

Pd nanoparticles on green support as dip-catalyst: a facile transfer hydrogenation of olefins and N-heteroarenes in water

Shaikh

2019

RSC Adv.

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Section: Introductionmentioning

confidence: 99%

Pd nanoparticles on green support as dip-catalyst: a facile transfer hydrogenation of olefins and N-heteroarenes in water

Shaikh

2019

RSC Adv.

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“…[10] Ap ractical and commonly applied method to access oxocarbenium ions is the elimination of al eaving group.I nt his equilibrium, if the leaving anion could be trapped by another molecule by molecular recognition, the formation of oxocarbenium ions would be favored. We recently developed ab ifunctional ligand, ZhaoPhos, [11] aiming to incorporate athiourea moiety on ab isphosphine ligand to render as econdary interaction with as ubstrate.A nion binding by thiourea with substrates assists to achieve high efficiencies and high enantioselectivities in homogeneous hydrogenation of cationic C=Nb onds present in iminium, [12] (iso)quinolinium, [13] and indolinium ions. [14] We envisioned that this type of highly reactive intermediate could be captured by thiourea [15] and be reduced by metal hydride complexes in an ionic hydrogenation manner.…”

Section: Introductionmentioning

confidence: 99%

Iridium‐Catalyzed Enantioselective Hydrogenation of Oxocarbenium Ions: A Case of Ionic Hydrogenation

et al. 2020

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Ionic hydrogenation has not been extensively explored, but is advantageous for challenging substrates such as unsaturated intermediates. Reported here is an iridium‐catalyzed hydrogenation of oxocarbenium ions to afford chiral isochromans with high enantioselectivities. A variety of functionalities are compatible with this catalytic system. In the presence of a catalytic amount of the Brønsted acid HCl, an α‐chloroether is generated in situ and subsequentially reduced. Kinetic studies suggest first‐order kinetics in the substrate and half‐order kinetics in the catalyst. A positive nonlinear effect, together with the half kinetic order, revealed a dimerization of the catalyst. Possible reaction pathways based on the monomeric iridium catalyst were proposed and DFT computational studies revealed an ionic hydrogenation pathway. Chloride abstraction and the cleavage of dihydrogen occur in the same step.

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“…[8a] If ac arbocation could be stabilized by either adjacent heteroatoms or substituents and therefore exist in considerable concentration,t he feasibility of being captured and subsequently reduced by am etal hydride would create an opportunity to form as tereogenic center.T his strategy offersa na lternative approacht op reparing chiral acetals by asymmetric hydrogenation.F ortunately,o ur group hasr ecently developed at hiourea-containing bis-phosphine ligand, ZhaoPhos, [9] which has the potential to bind with ionic substrates throughh ydrogen bonding. This catalytic system tolerates acidic conditions, [10] and has been successfully applied in the asymmetrich ydrogenation of imines, [11] quinolines/isoquinolines, [12] indoles, [10] and conjugated olefins. [13] Guided by these rationales, we envisioned that this catalytic system has the potential to achieve the asymmetric hydrogenation of cationic sp 2 carbon atoms to generate chiral acetal compounds.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Hydrogenation of Cationic Intermediates for the Synthesis of Chiral N,O‐Acetals

Sun

Zhao

Wang

et al. 2020

Chemistry A European J

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For over half a century, transition‐metal‐catalyzed homogeneous hydrogenation has been mainly focused on neutral and readily prepared unsaturated substrates. Although the addition of molecular hydrogen to C=C, C=N, and C=O bonds represents a well‐studied paradigm, the asymmetric hydrogenation of cationic species remains an underdeveloped area. In this study, we were seeking a breakthrough in asymmetric hydrogenation, with cationic intermediates as targets, and thereby anticipating applying this powerful tool to the construction of challenging chiral molecules. Under acidic conditions, both N‐ or O‐acetylsalicylamides underwent cyclization to generate cationic intermediates, which were subsequently reduced by an iridium or rhodium hydride complex. The resulting N,O‐acetals were synthesized with remarkably high enantioselectivity. This catalytic strategy exhibited high efficiency (turnover number of up to 4400) and high chemoselectivity. Mechanistic studies supported the hypothesis that a cationic intermediate was formed in situ and hydrogenated afterwards. A catalytic cycle has been proposed with hydride transfer from the iridium complex to the cationic sp2 carbon atom being the rate‐determining step. A steric map of the catalyst has been created to illustrate the chiral environment, and a quantitative structure–selectivity relationship analysis showed how enantiomeric induction was achieved in this chemical transformation.

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Strong Brønsted acid promoted asymmetric hydrogenation of isoquinolines and quinolines catalyzed by a Rh–thiourea chiral phosphine complex via anion binding

Abstract: Catalyzed by a Rh/bisphosphine–thiourea (L1) complex, isoquinolines and quinolines are hydrogenated with high conversions and high enantioselectivities.

Cited by 144 publications

References 34 publications

Pd nanoparticles on green support as dip-catalyst: a facile transfer hydrogenation of olefins and N-heteroarenes in water

Pd nanoparticles on green support as dip-catalyst: a facile transfer hydrogenation of olefins and N-heteroarenes in water

Iridium‐Catalyzed Enantioselective Hydrogenation of Oxocarbenium Ions: A Case of Ionic Hydrogenation

Asymmetric Hydrogenation of Cationic Intermediates for the Synthesis of Chiral N,O‐Acetals

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