Related Experiment Video
Updated: Jun 6, 2026
06:26
Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source
Published on: August 17, 2018
Development and application of versatile bis-hydroxamic acids for catalytic asymmetric oxidation
Allan U Barlan1, Wei Zhang, Hisashi Yamamoto
1Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois, 60637, USA.
Tetrahedron
|September 28, 2011
Summary
Researchers developed novel C(2)-symmetric bis-hydroxamic acid (BHA) ligands for asymmetric catalysis. These BHA ligands show versatility in vanadium-catalyzed epoxidation and molybdenum-catalyzed oxidation reactions.
Area of Science:
- Organic Chemistry
- Catalysis
- Asymmetric Synthesis
Background:
- Chiral ligands are crucial for enantioselective transformations in organic synthesis.
- Developing novel ligand scaffolds with broad applicability is an ongoing challenge.
- Bis-hydroxamic acid (BHA) ligands offer unique coordination properties.
Purpose of the Study:
- To design and synthesize novel C(2)-symmetric bis-hydroxamic acid (BHA) ligands.
- To evaluate the efficacy of these BHA ligands in vanadium-catalyzed asymmetric epoxidation.
- To explore the application of BHA ligands in molybdenum-catalyzed asymmetric oxidation reactions.
Main Methods:
- Synthesis of C(2)-symmetric bis-hydroxamic acid (BHA) ligands.
- Vanadium-catalyzed asymmetric epoxidation of allylic and homoallylic alcohols.
- Molybdenum-catalyzed asymmetric oxidation of unfunctionalized olefins and sulfides.
Main Results:
- Successful development of new C(2)-symmetric BHA ligands.
- Demonstrated high enantioselectivity in vanadium-catalyzed asymmetric epoxidation.
- Showcased the versatility of BHA ligands in molybdenum-catalyzed oxidation of olefins and sulfides.
Conclusions:
- The newly designed BHA ligands are effective catalysts for asymmetric oxidation reactions.
- BHA ligands exhibit broad applicability in both vanadium and molybdenum catalysis.
- These findings highlight the potential of BHA scaffolds in developing new asymmetric catalytic systems.
More Related Videos
Related Concept Videos
02:17Reduction 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...
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...
02:44Oxidation 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.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
02:36Regioselectivity 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.
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.
02:21Oxidation of Alkenes: Syn Dihydroxylation with Potassium Permanganate
Alkenes can be dihydroxylated using potassium permanganate. The method encompasses the reaction of an alkene with a cold, dilute solution of potassium permanganate under basic conditions to form a cis-diol along with a brown precipitate of manganese dioxide.