![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)
The Asymmetric Piers Hydrosilylation.
Lars Süsse1, Julia Hermeke1, Martin Oestreich1
1Institut für Chemie, Technische Universität Berlin , Strasse des 17. Juni 115, 10623 Berlin, Germany.
Journal of the American Chemical Society
|May 24, 2016
Summary
A novel chiral borane catalyst enables highly enantioselective hydrosilylation of acetophenone derivatives. This breakthrough asymmetric reaction achieves up to 99% enantiomeric excess (ee) without needing a Lewis base.
Area of Science:
- Organometallic Chemistry
- Asymmetric Catalysis
Background:
- The development of efficient asymmetric catalytic methods is crucial for synthesizing enantiomerically pure compounds.
- Borane catalysts, particularly those based on B(C6F5)3, have shown promise in carbonyl hydrosilylation reactions.
- Achieving high enantioselectivity often requires additional Lewis bases or complex catalyst systems.
Purpose of the Study:
- To develop a novel, highly enantioselective catalytic system for the hydrosilylation of acetophenone derivatives.
- To investigate an unprecedented asymmetric variant of Piers' B(C6F5)3-catalyzed carbonyl hydrosilylation.
- To explore the role of catalyst structure and reaction conditions in achieving high enantiomeric excess (ee).
Main Methods:
- Synthesis of an axially chiral, cyclic borane catalyst featuring a single C6F5 group.
- Application of the chiral borane catalyst in the enantioselective hydrosilylation of acetophenone derivatives using trihydrosilanes.
- Optimization of reaction conditions to maximize enantioselectivity and yield.
Main Results:
- The chiral borane catalyst successfully promoted the highly enantioselective hydrosilylation of acetophenone derivatives, achieving up to 99% ee.
- The reaction proceeded efficiently without the need for an additional Lewis base.
- Steric congestion from the 3,3'-disubstituted binaphthyl backbone and the use of reactive trihydrosilanes were identified as key factors for success.
Conclusions:
- An axially chiral, cyclic borane catalyst is effective for asymmetric carbonyl hydrosilylation.
- This method represents a significant advancement in asymmetric catalysis, offering a Lewis base-free route to enantiomerically enriched products.
- The catalyst design and choice of reducing agent are critical for achieving high enantioselectivity in this novel reaction.
Related Concept Videos
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
4.0K
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...
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...
4.0K
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
9.9K
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
9.9K
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
9.3K
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.
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.
9.3K
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
13.3K
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.
13.3K
02:40Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
11.3K
Introduction
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
11.3K
02:36Regioselectivity and Stereochemistry of Hydroboration
9.7K
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.
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.
9.7K