The Study On Electrocatalytic Minisci Acylation

Minisci Reaction is a free radical substitution reaction which an alkyl or acyl radical reacts with an aromatic compound,in particular with an electron deficient aromatic heterocyclic base compound.Minisci reaction is one of the best approaches to achieve the C-H bond functionalization of electron-poor nitrogen-containing heteroarenes.There have been other noteworthy uses of the reaction to introduce acetyl groups to give electron-poor nitrogen-containing heteroarenes.Among various Minisci reactions,acylation of N-heteroarenes has attracted more attention due to the wide occurring of the acylated adducts in many pharmaceutical compounds or serving as important intermediates in organic synthesis.While much efforts have been devoted to the Minisci acylations,most of the reported methods involves the utilization of transition metals,such as Ag as catalysts mainly,and excess amounts of toxic oxidants.In this paper,acyl radical,which is induced by the use of halogen under electrochemical conditions,is applied to synthesize the acylated adducts,to develop an environmentally friendly method to functionalize the C-H bonds of electron-poor nitrogen-containing heteroarenes.The paper conducted the following research:（1）Electrocatalytic Minisci acylation reaction of N-heteroarenes mediated by NH₄IAn electrochemical C-H acylation of electron-deficient N-heteroarenes withα-keto acids is reported.This first electrochemical Minisci acylation reaction proceeded using NH₄I as a redox catalyst.A broad N-heteroarenes scope and high functional group tolerance are observed.Selective monoacylation of N-heteroarenes is achieved via control of acyl radical at a low concentration.Results of cyclic voltammetry and control experiments disclose that the electrogenerated I₂ is likely the active species to initiate the oxidative decarboxylation of carboxylate anion via an acyl hypoiodite intermediate.The electrochemical Minisci acylation provides a straightforward approach for the late-stage functionalization of pharmacophores.（2）Electrochemical synthesis of acetylpyrazineAcetyl pyrazine has been widely used in the flavor industry,which is one kind of important flavor compounds and organic intermediates,but at present,there are many environmental problems about the synthesis of acetyl pyrazine,for example,harsh conditions,post-processing complex.It is very important to develop a new process route which is environmentally friendly.Electroorganic chemistry,which is a new kind green chemistry synthesis method,provides a practical approach to synthesis,and has received increasing attention.