Site-Selective C-H Functionalization of Carbazoles
Mazen Elsaid1, Robbie Ge1, Chong Liu1
1Department of Chemistry and Biochemistry, Texas Tech University, USA.
Angewandte Chemie (International Ed. in English)
|May 15, 2023
Summary
Researchers developed a new method for direct C-H alkylation and acylation of carbazoles using norbornene (NBE) as a temporary directing group. This bypasses the need for pre-installed groups, improving efficiency in synthesizing valuable carbazole compounds.
Area of Science:
- Organic Chemistry
- Catalysis
- Medicinal Chemistry
Background:
- Carbazole alkaloids are crucial in pharmaceuticals and material sciences.
- Current C1 functionalization methods for carbazoles require directing groups, limiting scope and efficiency.
Purpose of the Study:
- To develop a novel, direct palladium-catalyzed C-H functionalization of carbazoles.
- To introduce norbornene (NBE) as a transient directing mediator for carbazole C1 functionalization.
Main Methods:
- Direct palladium-catalyzed C-H alkylation of carbazoles.
- Direct palladium-catalyzed C-H acylation of carbazoles.
- Utilizing norbornene (NBE) as a transient directing mediator.
Main Results:
- Achieved direct C-H alkylation and acylation of carbazoles without pre-installed directing groups.
- Demonstrated the utility of norbornene (NBE) as an effective transient directing mediator.
- Identified a novel six-membered palladacycle intermediate in Pd/norbornene reactions.
Conclusions:
- This work presents the first direct Pd-catalyzed C-H alkylation and acylation of carbazoles using NBE.
- The findings offer a more efficient and versatile route for carbazole functionalization.
- The proposed palladacycle intermediate expands understanding of Pd/norbornene catalytic cycles.
Related Concept Videos
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
8.5K
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.
8.5K
02:10Carbocations
11.4K
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...
11.4K
02:36Regioselectivity and Stereochemistry of Hydroboration
8.2K
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...
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...
8.2K
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
14.4K
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
14.4K
01:11Nucleophilic Aromatic Substitution: Elimination–Addition
4.0K
Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as high temperatures or strong bases. The mechanism of substitution under such conditions involves the highly unstable and reactive benzyne intermediate. Benzyne contains equivalent carbon centers at both ends of the triple bond, each of which is equally susceptible to nucleophilic attack. This 50–50 distribution of products is...
4.0K
01:17Reactions of α-Halocarbonyl Compounds: Nucleophilic Substitution
3.4K
Nucleophilic substitution in α-halocarbonyl compounds can be achieved via an SN2 pathway. The reaction in α-haloketones is generally carried out with less basic nucleophiles. The use of strong basic nucleophiles leads to the generation of α-haloenolate ions, which often participate in other side reactions.
3.4K