Metal-Free Generation of γ-Cyanoalkyl Radicals by N-Heterocyclic Carbene Catalysis: Assembly of 6-Cyanoalkyl Phenanthridines

Abstract

A number of γ-cyanoalkyl radicals were generated by sustainable N-heterocyclic carbene catalysis in tin-, transition-meal-, and light-free conditions, followed by insertion into biaryl isonitriles, thus leading to the rapid assembly of a variety of diversely functionalized 6-cyanoalkyl phenanthridines. A preliminary mechanism study revealed that a single-electron transfer radical process was possibly involved.

Lead-free halide Cs2MnCl4:Cu+ as a new phosphor for efficient green light emission

“…12 The mixed halogen compound Rb 2 CdCl 2 I 2 is the first single component white light emitting material with an all-inorganic layered perovskite structure. 13 The low abundance radioactive K 2 CuBr 3 has shown great X-ray scintillation properties. 14 Researchers have prepared a blue-emitting powder with PLQY as high as 96% by doping Eu 3+ into KCaCl 3 , 15 and it also has higher thermal stability.…”

NHC-Catalyzed Regioselective Intramolecular Radical Cyclization Reaction for the Synthesis of Benzazepine Derivatives

“…On the basis of the above investigations and previous literature, a plausible mechanism is outlined in Scheme . First, α-carbon radical II was generated via a single-electron transfer (SET) process accompanied by NHC A′ .…”

“…On the basis of the above investigations and previous literature, a plausible mechanism is outlined in Scheme . First, α-carbon radical II was generated via a single-electron transfer (SET) process accompanied by NHC A′ . Next, radical II regioselectively adds to the C=C bond to afford the intermediate III , which can be oxidized by intermediate I to give the intermediate IV .…”

“…As a result, further exploration of the NHC-catalyzed reaction without active carbonyl-group-reliant substrates would be more attractive. Very recently, Wang and co-workers reported several NHC-catalyzed aldehyde-free mechanistic routes for the efficient construction of various functionalized N -heterocycles . Encouraged by these impressive advances, we envisaged that the NHC-catalyzed redox-neutral radical addition cascade would provide a facile strategy to benzazepine scaffold.…”

Redox-Neutral Cyclization of 2-Isocyanobiaryls through Photoredox/PPh3 Dual Catalysis

“…Among them, phenanthridine is a fundamental unit of many naturally occurring products, pharmaceuticals, and functionalized polycyclic heteroarenes. , For example, there are a series of bioactive alkaloids that are a part of the phenanthridine motif such as asiaticumine A, norsanguinarine, decarine, trispheridine, and lycobetaine (Figure ). Due to its significant potentials in pharmaceutical and material chemistry, the development of synthetic methods for the phenanthridine scaffolds has attracted considerable attention among chemists. , While the Bischler–Napieralski reaction provided the most common method to access phenanthridine compounds, recently disclosed methods to construct a phenanthridine core focus on the use of more efficient, economic, and user-friendly techniques such as transition-metal catalysis, , controllable radical chemistry, benign electrocatalysis, and mild photochemistry. ,, …”