Related Experiment Video
Updated: Jun 19, 2025
10:44
Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
10.7K
Cyclopropanation with Non-Stabilized Carbenes via Ketyl Radicals
Duong T Ngo1, Jacob J A Garwood1, David A Nagib1
1Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States.
Journal of the American Chemical Society
|July 25, 2024
Summary
This study introduces a new iron-catalyzed method for creating nonstabilized alkyl iron carbenes from aldehydes. This approach enables efficient and stereoselective cyclopropanation reactions with diverse alkenes.
Area of Science:
- Organic Chemistry
- Organometallic Chemistry
- Catalysis
Background:
- Accessing nonstabilized alkyl iron carbenes is challenging.
- Developing efficient catalytic methods for carbene generation is crucial for organic synthesis.
Purpose of the Study:
- To develop a simple and robust method for generating nonstabilized alkyl iron carbenes.
- To explore the utility of these carbenes in novel (2+1) cycloaddition reactions.
- To investigate the mechanism of this iron-catalyzed cyclopropanation.
Main Methods:
- Iron-catalyzed reaction using aliphatic aldehydes as carbene precursors.
- Stereoselective cyclopropanation with a wide range of alkenes.
- Mechanistic studies involving radical intermediates.
Main Results:
- Successful generation of nonstabilized alkyl iron carbenes.
- High efficiency and stereoselectivity in (2+1) cycloaddition reactions.
- Demonstrated tolerance to air and water, allowing for convenient handling.
- Coupling with diverse nucleophilic, electrophilic, and neutral alkenes.
Conclusions:
- A novel radical mechanism provides access to rare alkyl iron carbenes.
- The developed method offers a practical and versatile route to cyclopropanes.
- Mechanistic insights confirm the role of ketyl radicals and iron carbene intermediates.
More Related Videos
Related Concept Videos
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
1.9K
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
1.9K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
17.9K
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.
17.9K
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
3.7K
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
3.7K
01:27Radical Substitution: Allylic Bromination
5.0K
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...
5.0K
02:10Carbocations
11.1K
Carbocations are one of the reaction intermediates formed during several nucleophilic substitutions or elimination reactions. A carbocation is an electron-deficient species with the central carbon atom having six electrons and three bonded atoms. The central carbon in a carbocation is sp2 hybridized with trigonal planar geometry. It has an empty p orbital perpendicular to the plane of the structure that can accept electrons. Thus, carbocations act as strong electrophiles and may react with any...
11.1K
01:33Radical Reactivity: Intramolecular vs Intermolecular
1.7K
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak...
1.7K