Photocatalytic, Phosphoranyl Radical-Mediated N–O Cleavage of Strained Cycloketone Oximes

Abstract

A photoinduced, phosphoranyl radical-mediated protocol for the direct N–O cleavage of strained cycloketone oximes via a polar/SET crossover process was developed for the first time. This visible-light-driven direct N–O activation mode for oxime offers beneficial features such as streamlined synthetic process and versatile photochemical reactivities. Consequently, the alkenes and α-trifluoromethyl alkenes with varied electronic and structural features acted as competent radical receptors in this protocol, enabling facile accesses to a range of elongated cyano and/or gem-difluoroalkene-bearing compounds.

Phosphoranyl Radical Fragmentation Reactions Driven by Photoredox Catalysis

“…In 2019, Yang and co-workers reported the formation of oxime-containing phosphoranyl radicals 169 , themselves formed from the ionic attack of photocatalytically generated phosphine radical cations 81 by oximes 168 ( Scheme 20 ). 40 Upon β-scission, the phosphoranyl radical 169 would afford triphenylphosphine oxide and iminyl radical 170 . Within this study, cyclobutanone oximes were utilized, and therefore, upon formation of the iminyl radical 170 , a radical transposition occurred through a strain-relieving C–C single bond cleavage to deliver cyanoalkyl radical species 171 .…”

Radical reactions promoted by trivalent tertiary phosphines

“…28). 52 The N-O bond of the oxime molecule can be directly cleaved via this protocol. Various aliphatic nitriles were afforded in moderate to excellent yields from the oxime and alkene substrates under mild photoredox catalytic conditions (Fig.…”

Recent Developments in Radical Cross‐Coupling of Redox‐Active Cycloketone Oximes

“…Later, Yang and co‐workers presented a photo‐induced, phosphoranyl radical‐mediated coupling reaction of cycloketone oximes 183 with α‐CF 3 alkenes 184 (Scheme 63). [80] The reaction involved a reductive quenching pathway and PPh 3 proved to be the best reductant. This protocol represented a novel approach for the generation of iminyl radical and avoided derivatizations of substrate oximes.…”