N-Heterocyclic Carbene/Magnesium Cocatalyzed Radical Relay Assembly of Aliphatic Keto Nitriles

Abstract

An unprecedented N-heterocyclic carbene and magnesium cocatalyzed three-component acylcyanoalkylation of alkenes with cycloketone oxime esters and aldehydes is presented. This method displayed good scope generality, providing a transition-metal- and photoredox-free pathway to access various multifunctionalized aliphatic keto nitrile structures under mild reaction conditions. Moreover, this strategy is supposed to follow a radical relay mechanism via a single electron transfer event of a Mg/matched Breslow intermediate/oxime ester electron-donating acceptor (EDA) complex.

Critical Assessment of the Reducing Ability of Breslow‐type Derivatives and Implications for Carbene‐Catalyzed Radical Reactions**

“…proposed that Mg II cations coordinate and activate oxime esters, thus allowing to patch up the potential gap with Breslow enolates. [6b] Still, other protocols do not similarly involve hard oxophilic Lewis acids. The case of the reduction of iodoaryls in presence of thiazolylidene catalysts is especially spectacular, as reduction potentials of substrates [19] can be up to 1.5 V lower than the reported values for the oxidation potential of Breslow enolates.…”

Aerobic Oxidative EDA Catalysis: Synthesis of Tetrahydroquinolines Using an Organocatalytic EDA Active Acceptor

“…The mechanism for this reaction was not further investigated, although it could be possible that the EDA complex between 1 and 4 or 2 could be activated thermally to some degree, as has been reported for other systems. 57 , 58 …”

Photoinduced radical cascade cyclization of acetylenic acid esters with oxime esters to access cyanalkylated coumarins

“…However, the group of Selander recently reported the iron-catalyzed coupling of cyclobutanone oximes with silyl enol ethers, which has led to this substrate re-attracting the interest of chemists and quickly becoming a research hotspot. 16 Various other scavengers including alkenes, 17 alkynes, 18 aroyl chlorides, 19 allylic sulfones, 20 heterocycles, 21 aryl isonitriles, 22 enaminothiones, 23 carboxylic acids, 24 aldehydes, 25 and TMSCN 26 along with glycine derivatives 27 were employed to achieve C–C bond functionalization. Apart from C–C bond functionalization, C–S, 28 C–B or C–Se, 29 and C–N 30 bond formations were also explored in this context.…”