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Inspired by the pioneering work of Forrester [17–20], the Leonori and the Studer group took carboxylic acid‐containing oximes 42 and used them to generate functionalized imine and ketone derivatives 43–45 (Scheme 2.11) [36–38]. These processes were all based on a reductive quenching photoredox cycle and required basic conditions to trigger the SET oxidation of the carboxylate functionality (46). This event led to two β‐scissions extruding CO₂ and acetone and forming the corresponding iminyl radical 47. This species then underwent 1,5‐HAT and the incipient carbon radical 48 was intercepted and diversified with several radical trapping agents (X–Y) such as N‐chlorosuccinimide (NCS; chlorination, 43), selectfluor (fluorination, 44), and Michael acceptors (Giese addition, 45). A final electron transfer between the reduced photocatalyst and the Y· intermediate, generated upon atom transfer/addition, led to an overall redox‐neutral process. This approach for remote ketone functionalization tolerated important functionalities such as protected amines, heteroaromatics, free alcohols, and ester groups among others. Interestingly, in the case of NCS, the intermediate NH imine was directly intercepted by NCS before hydrolysis, leading to the corresponding N–Cl imines that showed remarkable stability.

Scheme 2.11 Site‐specific intermolecular γ‐C(sp³)–H functionalization of ketones via iminyl radicals.

Source: Jiang and Studer [36], Morcillo et al. [37], and Davies et al. [38].