Photoredox-Catalyzed Intermolecular Remote C–H and C–C Vinylation via Iminyl Radicals

Abstract

A unified strategy for intermolecular remote C(sp)-H and C-C vinylation of O-acyl oximes with vinyl boronic acids has been achieved. This strategy is enabled by photoreductive generation of iminyl radicals from O-acyl oximes under irradiation by visible light. The translocated carbon-centered radicals, which are generated from the iminyl radicals through 1,5-hydrogen atom transfer or C-C cleavage, can be vinylated with vinyl boronic acids. This strategy opens up a new approach to remote functionalization via C(sp)-H and C-C cleavage and provides an efficient and versatile solution to the synthesis of γ-vinylation of ketones and nitriles.

Functionalization of remote C(sp3)-H bonds enabled by copper-catalyzed coupling of O-acyloximes with terminal alkynes

“…In this context, redox-active acyclic 15 and cyclic 16 oxime derivatives, pioneered by Forrester and Zard, respectively, have been demonstrated to be versatile precursors of iminyl radicals under either oxidative or reductive conditions. Depending on the structure of oximes, the iminyl radicals can evolve to a carbon radical through either β-scission [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] or 1,5hydrogen atom transfer (1,5-HAT) process [33][34][35][36][37][38][39] . The resulting carbon radicals can then be trapped by radical acceptors, affording remote C(sp 3 ) functionalized alkylnitriles and ketones.…”

Remote C(sp3)−H Arylation and Vinylation of N‐Alkoxypyridinium Salts to δ‐Aryl and δ‐Vinyl Alcohols

“…As shown in Scheme , diverse aryl, alkyl and unsubstituted vinyl boronic acids reacted with a range of N ‐alkoxypyridinium salts to afford the corresponding vinylation products in good yields. Recently, the groups of Yu and Duan, respectively, reported an elegant γ‐vinylation of oxime esters by addition of the translocated carbon radicals to styrene or styrene‐derived boronic acids for the synthesis of γ‐vinyl ketones. However, only styrene and its derivatives were active as vinylating agents under their conditions .…”

“…Recently, the groups of Yu and Duan, respectively, reported an elegant γ‐vinylation of oxime esters by addition of the translocated carbon radicals to styrene or styrene‐derived boronic acids for the synthesis of γ‐vinyl ketones. However, only styrene and its derivatives were active as vinylating agents under their conditions . To the best of knowledge, the present method represents the first general method for the incorporation of a diversely substituted vinyl group into the δ position of the alcohols.…”

Iron‐Catalyzed Synthesis of Dihydronaphthalenones from Aromatic Oxime Esters

“…As early as in 1976, Forrester and co‐workers reported an iminyl radical‐mediated intramolecular 1,5‐H transfer arylation procedure which need visible light and strong oxidant (Scheme , A) . Since then, many procedures for selective C−C bond cleavage or remote C( sp 3 )−H activation– through iminyl radical intermediate were established by several groups. Recently, Nevado and Shu reported a visible‐light‐mediated intramolecular alkylation of remote aliphatic C−H bonds via 1,5‐HAT through an iminyl radical (Scheme , A) .…”