Photoredox Imino Functionalizations of Olefins

Abstract

Shownh erein is that polyfunctionalized nitrogen heterocycles can be easily prepared by avisible-light-mediated radical cascade process.T his divergent strategy features the oxidative generation of iminyl radicals and subsequent cyclization/radical trapping,whichallows the effective construction of highly functionalized heterocycles.T he reactions proceed efficiently at room temperature,u tilize an organic photocatalyst, use simple and readily available materials,a nd generate,i nas ingle step,v aluable building blocks that would be difficult to prepare by other methods.

Chemistry With N-Centered Radicals Generated by Single-Electron Transfer-Oxidation Using Photoredox Catalysis

“…Shortly after our report, the Leonori group also disclosed the generation of iminyl radicals via SET-oxidation of α-imino-oxy acids by using an acridine derivative as the photocatalyst (Scheme 18). 66 As in the example discussed in Scheme 17, the oxidatively generated iminyl radical undergoes efficient 5-exo cyclization and thus the generated nucleophilic alkyl radical of type 100 (see Scheme 17) then reacts with different radical trapping reagents. Along with simple reduction of 100 (H-transfer, see 104a), trapping with halo-(104b-e), azido-(104f), hydrazinyl-(104g), CF 3 S-(104h), PhS-(104i), PhSe-(104j), cyano-(104l), alkenyl-(104m), alkynyl-(104n), and alkyl-(104k) donors was achieved to give the corresponding pyrrolines in moderate to excellent yields.…”

Vinylbenziodoxol(on)es: Synthetic Methods and Applications

“…In 2017, the group of Leonori reported the first use of VBX reagents as partners in a free‐radical photoredox process mediated by acridinium dye 17 ( Scheme 7). [67] A nitrogen‐centered radical II was generated through a photoredox‐initiated decarboxylation of oxime precursors 15 via carboxy radical I , followed by cyclization to give alkyl radical III , which was trapped to furnish nitrogen heterocycles 16 . Ph‐VBX ( 2a ) was effectively employed as radical trap without erosion of the olefin ( E / Z ) ratio to give products 16a – 16f .…”

Light‐Driven Enantioselective Synthesis of Pyrroline Derivatives by a Radical/Polar Cascade Reaction

“…In one hand, it can be found the formation of iminyl radicals [6] by a photoinduced N À O bond cleavage. In response to this duty, the groups of Leonori, [7] Loh [8] and Studer, [9] have led this area (Figure 1 b, top). On the other hand, Molander and co-workers [10] efficiently developed a stratified synthesis of cyclic amines starting from alkyl silicates as radical precursors; disclosing a radical/polar crossover in the presence of N-substituted aldimines and ketimines (Figure 1 b, bottom).…”