Iminyl Radical‐Mediated Controlled Hydroxyalkylation of Remote C(sp³)‐H Bond via Tandem 1,5‐HAT and Difunctionalization of Aryl Alkenes

Abstract

A visible-light mediated g-hydroxyalkylation of ketones via C(sp 3 )-H functionalization has been developed under redox neutral conditions. This protocol relies on the iminyl radical-triggered 1,5-HAT followed by oxyalkylation of alkenes, wherein CÀC and CÀO bonds were constructed in one step. This three-component reaction features mild conditions, wide substrate scope and excellent functional group tolerance, thus providing a facile and highly efficient access to complex valuable ketones.

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.…”

Generation of Alkyl Radicals: From the Tyranny of Tin to the Photon Democracy

“…The use of water as the oxygen source was likewise used in the difunctionalization of aryl alkenes where the carbon-centered radical was formed by an intramolecular 1,5-HAT of a photogenerated iminyl radical. 178 …”

Oxime‐Derived Iminyl Radicals in Selective Processes of Hydrogen Atom Transfer and Addition to Carbon‐Carbon π‐Bonds

“…The synthesis of 6-alkoxy-6-aryl-ketones 20 from oxime esters 18 and styrenes 19 was carried out under similar conditions in the presence of alcohols (Scheme 9). [86] Cyclization of O- (2,4-dinitrophenyl)oximes 21 with SO 2 insertion was performed using diazobicyclooctane complex with SO 2 (DABSO) under blue light irradiation without the addition of any photocatalyst. It was assumed that the 2,4-dinitrophenyl group of oxime 21 forms photosensitive complex A with DABSO, which produces iminyl radical C and radical-cation B upon photolysis.…”

“…The synthesis of 6‐alkoxy‐6‐aryl‐ketones 20 from oxime esters 18 and styrenes 19 was carried out under similar conditions in the presence of alcohols (Scheme 9). [86] …”