Photoredox/Nickel‐Catalyzed Single‐Electron Tsuji–Trost Reaction: Development and Mechanistic Insights

Abstract

A regioselective, nickel-catalyzed photoredox allylation of secondary, benzyl, and α-alkoxy radical precursors is disclosed. Through this manifold, a variety of linear allylic alcohols and allylated monosaccharides are accessible in high yields under mild reaction conditions. Quantum mechanical calculations [DFT and DLPNO-CCSD(T)] support the mechanistic hypothesis of a Ni(0) to Ni(II) oxidative addition pathway followed by radical addition and inner-sphere allylation.

Regiodivergent Hydroaminoalkylation of Alkynes and Allenes by a Combined Rhodium and Photoredox Catalytic System

“…[10] Unfortunately,d espite those advances,o nly linear allylic products could be synthesized until now. [11] Thes elective generation of branched allylic derivatives is still an inherent challenging task for such radical involving allylation reactions. Given that after single electron oxidation, the neutral amine is converted into the radical cation, which will greatly acidify the C À Hbonds adjacent to the nitrogen atom.…”

Nickel‐Catalyzed Allylic Substitution Reactions: An Evolving Alternative

“…The field of dual Ni/photoredox catalysis was pioneered by the group of Molander, who used carbon radicals derived from trifluoroborate salts and 1,4-dihydropyridines (DHPs) in the presence of vinyl epoxides under a photoredox regime. [46] DFT calculations supported a Ni(0)-Ni(II)-Ni(III) redox sequence and an inner-sphere reductive elimination, although a Ni(0)-Ni(I)-Ni(III) pathway may also operate under different conditions (Scheme 22). A linear regioselectivity was observed in this allylic alkylation process, although for certain substrates the branched product could be observed in minor amounts.…”

A Retrosynthetic Approach for Photocatalysis

“…Similarly, dual catalysis has been employed for alkene synthesis starting from other alkyl radical precursors such as trifluoroborate salts, 4‐alkyl‐1,4‐dihydropyridines, α‐amino acids, N ‐arylamines, carboxylic acids or even unactivated alkyl bromides …”