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Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Reduction of Alkenes: Catalytic Hydrogenation02:13

Reduction of Alkenes: Catalytic Hydrogenation

Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide02:44

Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide

Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation02:24

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Regioselectivity and Stereochemistry of Hydroboration02:36

Regioselectivity and Stereochemistry of Hydroboration

A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydrogen Bonds00:26

Hydrogen Bonds

Hydrogen BondsHydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, and has a partial negative charge. The other is a hydrogen atom that has bonded with another electronegative atom and has a partial positive charge.Hydrogen Bonds Control the World!Because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom, such as oxygen or nitrogen, electrons in the bond are...

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Pioneering perspectives on asymmetric hydrogenation.

Accounts of chemical research·2007
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Updated: Jun 20, 2026

Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes
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Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes

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Asymmetric hydrogenations (Nobel lecture).

William S Knowles1

  • 1wsk9656@aol.com

Angewandte Chemie (International Ed. in English)
|September 15, 2009
PubMed
Summary

Chiral phosphine ligands enable asymmetric hydrogenation of prochiral olefins. While the exact mechanism remains elusive, these catalysts provide access to diverse chiral compounds.

Area of Science:

  • Organic Chemistry
  • Catalysis
  • Asymmetric Synthesis

Background:

  • The development of asymmetric hydrogenation catalysts originated from modifying Wilkinson's catalyst with chiral ligands.
  • The goal was to achieve enantioselective hydrogenation of prochiral olefins.

Discussion:

  • Early research, notably by Knowles, focused on chiral phosphorus ligands like (R,R)-DIPAMP, hypothesizing the phosphorus atom's central role in selectivity.
  • This hypothesis was challenged by the advent of ligands featuring chiral carbon backbones.
  • The precise mechanism of phosphine ligand action in asymmetric hydrogenation is still under investigation.

Key Insights:

  • Chiral phosphine ligands are crucial for high enantiomeric excess in asymmetric hydrogenation.
  • Ligands with chiral carbon backbones also facilitate asymmetric hydrogenation, broadening catalyst design.

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Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes
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  • Despite mechanistic uncertainties, these ligands offer a versatile route to chiral molecules.

    • Outlook:

    • Further research into the mechanism of action for phosphine ligands in asymmetric hydrogenation is warranted.
    • Exploration of novel chiral ligand designs, including those with chiral carbon backbones, will continue to advance the field.
    • The development of efficient and selective asymmetric hydrogenation catalysts remains a key objective in synthetic chemistry.