Related Experiment Video
Updated: May 11, 2026
![[(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)
[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst
Published on: May 21, 2019
Photocatalytic Regioselective Alkylation of 4-Alkenylpyridines via Delocalized Pyridinyl Radicals
Kemeng Du1, Zhichao Zhang1, Zehua Zhou1
1School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, China.
Abstract:
The control of selectivity in delocalized radical systems remains a formidable challenge in synthetic chemistry. We report a photocatalytic strategy for the regioselective alkylation of 4-alkenylpyridines using 4-alkyl-1,4-dihydropyridines (alkyl-DHPs) as radical precursors. The reaction proceeds via delocalized pyridinyl radicals, enabling radical-radical cross-coupling that delivers C6-alkylated products with exclusive regioselectivity, contrasting with the C4-selective pathway observed for simple pyridinyl radicals. Mechanistic studies and DFT calculations reveal that reversible formation of an unstable C4-coupled intermediate funnels the reaction toward the thermodynamically favored C6 pathway.
More Related Videos
09:54Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes
Published on: September 12, 2018
06:49Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst
Published on: April 22, 2016
Related Concept Videos
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
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.
Radical Anti-Markovnikov Addition to Alkenes: Overview
Preparation of Alkynes: Alkylation Reaction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
α-Alkylation of Ketones via Enolate Ions
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.
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.