Bisphosphine-Cobalt(II)-Catalyzed C(sp2)-O Bond Activation in Kumada Arylation of Heteroaryl Ethers
Khanh Truong Chau1, L Reginald Mills1
1Department of Chemistry, University of Houston, Houston, Texas77204-5003, United States.
Abstract:
Synthesized from benzothiazolones, 2-alkoxy benzothiazoles served as competent C(sp2)-O electrophiles in (bisphosphine)cobalt(II)-catalyzed Kumada arylation, forming 2-arylbenzothiazole products. Employing catalytic (5 mol %) bis(diphenylphosphino)propane (dppp)-cobalt(II) dibromide precatalyst, the Kumada arylation of heteroaryl ethers was general toward 2-alkoxybenzoxazole, 2-alkoxyquinoline, and 2-alkoxythiazole substrates (17-78% yield). Investigation of catalytically relevant precatalysts indicated kinetic incompetence of cobalt(I) and cobalt(0) complexes, supporting the proposal of a redox-neutral cobalt(II)-catalyzed reaction involving rate-determining heteroaryl ether substitution.
Related Concept Videos
Aldehydes and Ketones to Alkenes: Wittig Reaction Mechanism
The reaction begins with the nucleophilic addition between a phosphorus ylide and the carbonyl compound. Due to its carbanionic character, phosphorus ylide acts as a strong nucleophile and attacks the electrophilic carbonyl group. This generates a charge-separated dipolar intermediate called betaine. The negatively charged oxygen atom and...
Aldehydes and Ketones to Alkenes: Wittig Reaction Overview
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
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.
α-Bromination of Carboxylic Acids: Hell–Volhard–Zelinski Reaction
Aldol Condensation with β-Diesters: Knoevenagel Condensation
Regioselectivity and Stereochemistry of Hydroboration
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.
![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)
![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)