Dual Photoredox/Cobaloxime Catalysis for Cross-Dehydrogenative α-Heteroarylation of Amines

Abstract

We report a dual-catalytic platform for the crossdehydrogenative-coupling between (benzo-)thiazoles and amines which combines low loadings of an iridium photoredox catalyst and a cobaloxime catalyst under blue light irradiation. This transformation occurs without stoichiometric oxidants, giving products in moderate to excellent yields. DFT calculations support the key role of Co(II) for rearomatization of the radical-addition intermediate to generate the product.

Electrochemical Dehydrogenative C−H Aminomethylation of Imidazopyridines and Related Heterocycles

“…Based on the above‐mentioned results and literature reports, [15–19] a plausible mechanistic pathway is outlined in Scheme 5. First, one electron anodic oxidation of N,N,4‐trimethylaniline 2 a would lead to the radical cation I .…”

“…Moreover, their scope is usually limited in terms of functional group and heterocyclic tolerance. Recently, some photocatalytic techniques have enabled remarkable methods for the direct functionalization of α‐amino C−H bonds [15,16] . In addition, several research groups have also reported electrochemical solutions [17–19] .…”

Dual Photoredox and Cobalt Catalysis Enabled Transformations

“…From the results of several control experiments and spectroscopic studies, author proposed a tentative mechanism for this transformation (Figure 12 In 2021, Teskey group reported a potential merger of the Ircatalyzed photoredox process with Co-catalyzed cross dehydrogenative α-heteroarylation of amines without stoichiometric oxidants at low catalyst loadings. [29] Under the reaction condition, α-amino radicals generated selectively at the methyl position and even this selectivity remains with cyclohexyl containing amines. Apart from acyclic amines, cyclic amines such as N-phenyl pyrrolidines undergoes this reaction to give product in good yield.…”

“…In 2021, Teskey group reported a potential merger of the Ir‐catalyzed photoredox process with Co‐catalyzed cross dehydrogenative α ‐heteroarylation of amines without stoichiometric oxidants at low catalyst loadings [29] . Under the reaction condition, α ‐amino radicals generated selectively at the methyl position and even this selectivity remains with cyclohexyl containing amines.…”

Late-Stage N-Me Selective Arylation of Trialkylamines Enabled by Ni/Photoredox Dual Catalysis

“…We started our investigation by conducting arylation of N -Me piperidine with 4-bromobenzonitrile under Ni/photoredox conditions . Gratifyingly, when reaction occurs, we observe exclusive N -Me arylation product 1 .…”