O-Perfluoropyridin-4-yl Oximes: Iminyl Radical Precursors for Photo- or Thermal-Induced N–O Cleavage in C(sp²)–C(sp³) Bond Formation

Abstract

O-Perfluoropyridin-4-yl group was first installed onto cycloketone oximes as a new electrophore, which was proven to be efficient iminyl radical precursors under photocatalytic and thermal conditions. A range of O-perfluoropyridin-4-yl oximes were successfully utilized in C­(sp2)–C­(sp3) bond formations of quinoxalin-2­(1H)-ones and alkenes, providing facile accesses to a range of functionalized alkylnitriles.

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

“…At the same time, Xu and co‐workers reported that the cyanoalkylation of quinoxalinones could also be conducted in DMF with fac ‐Ir(ppy) 3 as the photocatalyst [66] . Recently, Yang and co‐workers have realized cyanoalkylation of quinoxalinones by using O ‐perfluoropyridinn‐4‐yl oximes as the cyanoalkyl source [67] . Guided by the same principle, Xia and co‐workers discovered that the cyanoalkylation protocol could be extended to other nitrogen‐bearing heterocycle including isoquinolines and quinolines [68] …”

“…[66] Recently, Yang and co-workers have realized cyanoalkylation of quinoxalinones by using O-perfluoropyridinn-4-yl oximes as the cyanoalkyl source. [67] Guided by the same principle, Xia and coworkers discovered that the cyanoalkylation protocol could be extended to other nitrogen-bearing heterocycle including isoquinolines and quinolines. [68] A radical cascade cyclization of aryl isonitriles 156 and cycloketone oxime esters 155 with fac-Ir(ppy) 3 as the photocatalyst in DMAc was demonstrated by Zhang and co-workers (Scheme 53).…”

Recent Advances in Photocatalytic Functionalization of Quinoxalin‐2‐ones

“…To conclude the reports on photoredox-triggered cyanopropylation of quinoxalin-2-ones using redox-active cyclobutanone oxime esters, at early 2020, Yang's research team reported a synthetic protocol. [36] In the abovementioned work, a set of γcyanopropylated quinoxalin-2-ones were synthetized using a perfluoropyridin-based redox active cyclobutanone oxime. Although they only described sixteen quinoxalin-2-one-derived examples (Scheme 14), they conducted a lot of experiences in order to gain insight in the reaction mechanism, as well as a comparison of the generation of the desired radical under thermal reaction conditions.…”

“…In just six months, four similar methodologies were reported and, surprisingly, the first one in the chronological line was the most sustainable, because of the use of Eosin Y as photoredox catalyst, avoiding the use of expensive and toxic metals complexes. Regarding the scope of the reaction, the two Xin Li's works showed a broad scope, particularly in the design and use of complex redox-active oximes, while the labour of Yang [36] and collaborators goes deeper into the mechanistic aspects of this transformation.…”

“…Scheme 22. C-3 Direct alkylation of quinoxalin-2-ones using 2D-COD-1 as heterogeneous photocatalyst (Yang, 2020).…”