Electrochemical Oxidative Functionalization Via Difluoromethyl Radical And Radical Cation

Carbon centered radicals and radical cations of ? systems are important reactive intermediates for forging C-C and C-heteroatom bonds.Electroorganic synthesis,which is a green synthetic tool,provides a powerful method for the access of various reaction radical and ionic intermediates.In this thesis,we have developed electricitypowered difluoromethylation of alkynes,alkynylation of alkenes,and selective oxidation of methylarenes.In the first part,a new difluoromethylation reagent,CF2HSO2NHNHBOC,has been synthesized in one step from commercial reagents.Based on this reagent,a rarely reported radical difluororriethylarylation of alkynes has been developed through ferrocene-mediated electrochemical oxidation,leading to a challenging 7-membered ring-forming homolytic aromatic substitution and direct preparation of pharmacologically active benzoazepines skeleton.In the second part,high regio-and chemoselective hydroxy-alkynylation of aryl alkenes have been developed through electrochemically enabled addition of organotrifluoroborate reagent and H2O across the double bond of the alkene.This electrochemical oxidative reaction not only obviates the need for transition metal catalysts and oxidizing reagents but also breaks through the limitation of traditional methods in chemical selectivity.In the third part,we report selective electrochemical oxidation of polymethylbenzimidazole and successfully synthesized aromatic aldehydes without using oxidant reagent.Benzylic oxygenation of methylarenes is a highly attractive method for aldehyde synthesis as the starting materials are easy to obtain and handle.However,regioselective oxidation of functionalized methylarenes,especially those that contain heterocyclic moieties,to aromatic aldehydes remains a significant challenge.Our method is not limited to traditional toluene oxidation,extended to various complex heterocyclic structures,which greatly broadens the types of oxidation substrates.More importantly,our method achieves a single methyl oxidation with high selectivity when contained multiple methyl groups or benzylic positions.