Visible‐Light‐Mediated Aromatic Substitution Reactions of Cyanoarenes with 4‐Alkyl‐1,4‐dihydropyridines through Double Carbon–Carbon Bond Cleavage

Abstract

Novel aromatic substitution reactions of cyanoarenes with 4‐alkyl‐1,4‐dihydropyridines as alkylating reagents in the presence of a catalytic amount of a photoredox catalyst proceed smoothly to give the corresponding alkyl‐substituted arenes in good to high yields. The present reaction system realizes a novel C−C bond‐forming reaction between two fragments generated from the C−C bond‐cleavage reactions of two independent substrates.

1,4-Dihydropyridines as Alkyl Radical Precursors: Introducing the Aldehyde Feedstock to Nickel/Photoredox Dual Catalysis

“…We believe that the homolysis of the DHP unit occurs via formation of a radical cation, followed by a deprotonation step, forming an aminyl radical that will then undergo homolysis. 15,16 Notably, we observed that 1c- N -Me (the N -methylated analogue of 1c ) failed to deliver the cross-coupling product under reaction conditions, thus supporting the deprotonation prior to the C–C cleavage event hypothesis. 15a …”

Alkyl‐C‐C‐Bindungsbildung durch Nickel/Photoredox‐Kreuzkupplung

“…[51,52] [52] die in Umwandlungen reagieren kçnnen, wie beispielsweise aromatischer Substitution. [53] Zwei Arbeitsgruppen [54,55] berichteten über die Kreuzkupplung von Arylhalogeniden und Alkyl-DHPs.E ine Gruppe verwendete eine Base zur Deprotonierung des DHP und Bildung einer leichter oxidierbaren anionischen Spezies (Schema 4A). Die zweite Arbeitsgruppe setzte anstelle der Base den oxidativeren 4CzIPN-Photokatalysator 4 ein (Abbildung 1).…”

Nickel‐ and Photoredox‐Catalyzed Cross‐Coupling Reactions of Aryl Halides with 4‐Alkyl‐1,4‐dihydropyridines as Formal Nucleophilic Alkylation Reagents

“…[11,12] These alkylation reagents have been used in photochemical reactions [11a, 12] and thermal reactions with Lewis acid catalysts [11b] or radical initiators. [12,14] In this reaction system, ak ey step is the generation of alkyl radicals as reactive intermediates by single-electron oxidation of 4-alkyl-1,4-dihydropyridines. [12,14] In this reaction system, ak ey step is the generation of alkyl radicals as reactive intermediates by single-electron oxidation of 4-alkyl-1,4-dihydropyridines.…”