Zinc Chelate Complexes of N‐Acyl Hydrazones as Substrates for Addition of Alkyl and Fluorinated Radicals

Abstract

Zinc chelate complexes can be generated in situ from N‐acyl hydrazones by treatment with isopropyl zinc iodide. These complexes couple with alkyl and fluorinated radicals under photoredox conditions. Alkyl radicals were generated from organozinc halides using an organic photocatalyst and afford hydrazines as a result of reductive mode of addition. Fluorinated radicals were formed from perfluorinated alkyl iodides under photoredox conditions leading to fluoroalkylated hydrazones via neutral reaction pathway.

Radical Substitution of Polyfluoroarenes and Heteroarenes Promoted by Photoredox Activation of Organozinc Iodides

“…Recently, we have described that organozinc reagents serve as excellent sources of alkyl radicals upon photocatalytic single electron oxidation [33–35] . Herein we report that organozincs can efficiently couple with perfluorinated aromatics and benzothiazole and benzoxazole derivatives (Scheme 1C).…”

“…[31,32] Recently, we have described that organozinc reagents serve as excellent sources alkyl radicals upon photocatalytic single electron oxidation. [33][34][35] Herein we report that organozincs can efficiently couple with perfluorinated aromatics and benzothiazole and benzoxazole derivatives (Scheme 1C). While organozinc reagents are widely used as nucleophilic reagents, [36][37][38][39][40] they are considered to be relatively weak nucleophiles.…”

One-Pot Transformation of Aldehydes to Ketones via Minisci-Type Reaction of Imines

“…At the same time, among a variety of azomethines, N -alkyl-substituted imines are the least reactive substrates in radical reactions, , and only recently we have succeeded in performing reductive radical addition to these imines . This was achieved by Lewis acidic activation of the CN bond, which markedly facilitates the attack by alkyl radicals. − Herein we report that similar to the Minisci reaction, N -alkyl imines under acidic conditions effectively couple with radicals leading to C–H functionalized products at the azomethine center (Scheme D). Since imines may be readily generated from aldehydes and the primary products may be hydrolyzed to ketones, the whole sequence may be performed in one pot.…”

C–O Coupling of Hydrazones with Diacetyliminoxyl Radical Leading to Azo Oxime Ethers—Novel Antifungal Agents

“…However, ionic mechanisms were proposed for oxidative cyclizations of α,β-unsaturated N-tosylhydrazones in some cases [8,10]. It should also be noted that in some functionalizations of type A (Scheme 1A), an additional synthetic step of chelate complex formation was necessary for effective radical functionalization of hydrazones [11][12][13]. Hydrazones are reported to undergo peroxidation by t-BuOOH in the presence of cobalt-salen complexes with the formation of geminal azoperoxides and geminal azoxyperoxides [14].…”