Transformable Directing Groups Assisted Transition- Metal-Catalyzed Aromatic C-H Functionalization

Directing groups assisted transition-metal catalyzed C-H activation is emerging as a hot topic in organic synthetic chemistry. Besides the coordination ability to direct regioselective C-H activation, chemists paid increasing attentions to the diverse transformation functions of directing groups in synthetic chemistry recently. Thus, it is of great importance to develop multitasking directing groups with practical synthetic utilility. Based on current research background, this dissertation was focused on the development of novel C-H functionalizations directed by easily removable or modifiable directing groups, including Weinreb amide, azobenzene, and N-nitroso etc.This dissertation includes five chapters.Chapter 1:IntrodutionThe importance of directing groups for C-H activation was briefly introduced firstly. Recent examples on readily removable/modifiable directing groups assisted C-H functionalizations and their synthetic applications were next overviewed, in which the directing groups were categorized according to the coordination atoms chelated with transition metals.Chapter 2:Rh(III)-catalyzed C-H olefination of aryl Weinreb amidesWeinreb amide has been developed as an efficient directing group for rhodium-catalyzed regioselective olefination of aromatic C-H bond. While Weinreb amide has been demonstrated as an easily installed and removable/modifiable functional groups, this transformation showed potential synthetic prospect.Chapter 3:Pd(II)-catalyzed C-H arylation directed by Weinreb amidesTo further expand its application as directing group, Weinreb amide has been applied to palladium-catalyzed C-H arylation, where aryl iodide was used as coupling reagent. This protocol exhibits mild reaction conditions, broad substrates scope and good functional groups compatibility.Chaper 4:Rh(III)-catalyzed synthesis of 2-Aryl-2H-Benzotriazoles from azoarenes and IBA-N3A novel method for Rh-catalyzed facile synthesis of 2-aryl-2H-benzotriazoles using simple azobenzenes as substrates and azidobenziodoxolone as azide source. It is the first time that azidobenziodoxolon reagents were used on directing groups assisited transition-metal catalyzed C-H activation. This reaction tolerates both symmetric and unsymmetric azobenzenes. This method has also been successfully applied for the synthesis UV-absorber Tinuvin P.Chapter 5:Rh(III)-catalyzed C-H Arylation of N-nitrosoanilinesThe easily modifiable N-nitroso functional group has been developed as directing group for rhodium-catalyzed C-H arylation with commercially available aryl boronic acid as coupling partner. This reaction provides an efficient method for rapid construction of ortho-amine substituted biaryl motif.