This minireview highlights the recent advances in the chemistry of Hantzsch esters in photoredox catalyzed organic synthesis, with particular emphasis placed on reaction mechanisms.

A room-temperature, visible-light-driven N-centered iminyl radical-mediated and redox-neutral C-C single bond cleavage/radical addition cascade reaction of oxime esters and unsaturated systems has been accomplished. The strategy tolerates a wide range of O-acyl oximes and unsaturated systems, such as alkenes, silyl enol ethers, alkynes, and isonitrile, enabling highly selective formation of various chemical bonds. This method thus provides an efficient approach to various diversely substituted cyano-containing alkenes, ketones, carbocycles, and heterocycles.

No abstract

The construction of carbon–heteroatom bonds is one of the most active areas of research in organic chemistry because the function of organic molecules is often derived from the presence of heteroatoms. Although considerable advances have recently been achieved in radical-involved catalytic asymmetric C–N bond formation, there has been little progress in the corresponding C–O bond-forming processes. Here, we describe a photoinduced copper-catalyzed cross-coupling of readily available oxime esters and 1,3-dienes to generate diversely substituted allylic esters with high regio- and enantioselectivity (>75 examples; up to 95% ee). The reaction proceeds at room temperature under excitation by purple light-emitting diodes (LEDs) and features the use of a single, earth-abundant copper-based chiral catalyst as both the photoredox catalyst for radical generation and the source of asymmetric induction in C–O coupling. Combined experimental and density functional theory (DFT) computational studies suggest the formation of π-allylcopper complexes from redox-active oxime esters as bifunctional reagents and 1,3-dienes through a radical–polar crossover process.

A photoinduced, copper-catalyzed three-component radical cross-coupling of cycloketone oxime esters, alkenes, and terminal alkynes is described for the first time. Key to the success of this process was the integration of photoinduced iminyl radicalmediated C−C bond cleavage with the conceptual simplicity of copper-catalyzed radical cross-coupling. This protocol provides access to cyanoalkyl-containing propargylic compounds in good yields.

Kharasch-Sosnovsky reaction is one of the most powerful methods for allylic oxidation of alkenes.H owever, the inherent radical mechanism and use of peroxides as both oxidants and oxygen nucleophiles render dearth of universal catalytic systems for highly enantioselective variants and limited scope.H erein, an alternative to the asymmetric Kharasch-Sosnovsky reaction that utilized ac hiral copper catalyst and purple-LED irradiation to enable the threecomponent coupling of 1,3-dienes,oxime esters,and carboxylic acids is reported. This protocol features mild conditions, remarkable scope and functional group tolerance as evidenced by > 80 examples and utility in the late-stage modification of pharmaceuticals and natural products.D etailed mechanistic studies provide evidences for the radical-based reaction pathway.Scheme 1. Classic Kharasch-Sosnovsky reaction and design of an alternative to the asymmetric Kharasch-Sosnovsky-type reaction.

Catalytic enantioselective chemical reactions involving highly reactive radical species remain largely unexplored. We report herein for the first time a novel enantioselective radical ring-opening cyanation of redox-active oxime esters by dual photoreodox and copper catalysis. This mild protocol shows good functional group tolerance and broad substrate scope, producing a wide range of optically active alkyl dinitriles with high yields and excellent enantioselectivities, which are difficult to access traditionally.

A photoredox-catalyzed iminyl radical-triggered C–C bond cleavage/addition/Kornblum oxidation cascade of cycloketone oxime esters and styrenes in DMSO is described for the first time.