Studies On Free Radical Specees Involved C-H Bond Activation Reactions

Transition metal-catalyzed C-H bond activation has played an important role in the construction of new chemical bonds such as C-C and C-S bonds over the past few decades.Compared with the traditional transition metal-catalyzed coupling reactions,the direct functionalization of C-H bonds avoids the preafunctionalization of the substrates,and has obvious advantages in terms of atomic economy and so on.Therefore,in recent years,C-H bond activation reaction has become a hot topic for chemists.On the basis of previous work,this thesis focuses on the study of radical species-involved C-H bond activation reaction.The main contents are divided into the following three sections:1.The C-S bond formation reaction under metal-free conditions was studied.In this reaction,the C-S bond was successfully constructed via NH4I-catalyzed direct thiomethylation of sp2 C-H bond in ?-oxoketene dithioacetals by the use of cheap dimethyl sulfoxide as the source of thiomethyl group.The reaction has advantages of the use of cheap and easily availabe DMSO as the source of the thiomethyl group and good compatibility of substrates.2.The palladium-catalyzed intramolecular oxidative cross-coupling/annulation reaction of o-alkynyl benzaldehydes was studied.The reaction can lead to different chemoselectivity by fine tuning of the reaction conditions.Thus,in the presence of the Pd?OAc?2/TBHP/THF system,the reaction underwent an intramolecular hydroaroylation of alkyne moiety to give indenone derivatives in high yields,selectivity and atom economy;while in the presence of the Pd?OAc?2/TBHP/CH3CN/NaOAc system,the reaction underwent an TBHP-participated nucleophilic addition/annulation reaction to give peroxy bond containing isochroman derivatives in high selectivity,atom economy and simple operation.3.The Cu?NO₃?2.3H₂O-promoted decarbonylative nitration of ?,?-unsaturated aldehydes for the synthesis of nitroolefin compounds was studied.The reaction has advantages of the use of neutral reaction conditions,easy availability of the starting materials,simple operation and good compatibility of substrates.