Synthesis Of Dibenzo [a,f] Quinolizine Derivatives And Chiral Fluorinated Compounds Via Direct Functionalization Of C-H Bonds

C-H bonds widely exist in all kinds of organic compounds, including natural gas, petroleum, plastics and proteins. Direct functionalization of C-H bond not only brings a new impetus for the development of organic synthesis, but also provides a more concise synthesis tool for related scientific research, such as medicine, biology, materials and so on. In recent years, C-H bond direct functionalization has intrigued many researchers, and many breakthroughs have been achieved in radical hydrogen extraction, metal carbene insertion of C-H bond, directing group assisted transition metal C-H bond activation, which gradually became the direct and effective tool for the modification and transformation of various hydrocarbons. As a continuing program to our group’ study in C-H functionalization research, this thesis mainly centered on the following three chapters involving synthesis of heterocyclic compounds and asymmetric fluorination via direct funcationalization of C-H bonds:Part I: This chapter firstly introduced the properties of C-H functionalization in various organic compounds and the classifications of the reaction of C-H functionalization. Then, the recent advances in the field of C–H Bond functionalization in complex organic synthesis were describes, including free radical hydrogen extraction type C-H bond functionalization, transition metal–catalyzed carbene and nitrene insertion of C-H bond and C–H functionalization by means of coordination-directed metalation. Additionally, the advent and outlook in the field of C-H functionalization was also described.Part II: This chapter firstly descibed the recent advances of visible-light photocatalysis and C–H bond functionalization involving visible-light photoredox catalysis, respectively. Then, we presented a dual C-H functionalization of N-aryl tetrahydroisoquinolines via merging visible-light photocatalytic oxidation and inverse electron-demand aza-Diels-Alder reaction, which provided an efficient way to construct dibenzo[a,f]quinolizine skeleton. A series of tetrahydroisoquinolines with substituents on both N-aryl ring and tetrahydroisoquinoline ring were smoothly converted into the corresponding dibenzo[a,f]quinolizine derivatives. A wide range of dienophiles were also tested under the optimal conditions. Finally, we proposed a plausible reaction mechanism to describe this transformation.Part III: This chapter firstly presented the recent progress on catalytic fluorination of Sp2 C-H bond and asymmetric fluorination of Sp3 C-H bond, respectively. Next, we described a catalytic enantioselective α-fluorination of acyclic ketones via chiral iridium complex catalysis, which provided an efficient way to get α-fluorination of 2-acyl imidazoles. A variety of 2-acyl imidazoles could be smoothly converted into the corresponding products by this asymmetric fluorination strategy. To demonstrate the potential utility of this methodology, we also tested a 1 mmol scale synthesis of fluoride product. The reaction proceeded smoothly to afford the corresponding product with excellent results. Finally, a plausible catalytic mechanism was outlined to present this reaction.