Rh(Ⅲ)-/Co(Ⅲ)-Catalyzed Coupling Of Arenes With Unsaturated Substrates Via C-H Bond Activation

Over the past decades, transition metal-catalyzed C-H functionalization has been developed as an efficient and versatile approach for the formation of carbon-carbon or carbon-heteroatom bonds. Rh(Ⅲ) and Co(Ⅲ) catalysts have been widely employed for C-H activation owing to their high activity, good selectivity, broad scopes and good functional group tolerance. This dissertation starts with a review of Rh(Ⅲ)- and Co(Ⅲ)-catalyzed C-H activation and functionalization of arnenes. The studies mainly focused on Rh(Ⅲ)-catalyzed sulfonylation, amidation, halogenation, annulation reactions with alkynes, and Co(Ⅲ)-catalyzed amination-cyclization of arenes.1. Rh(Ⅲ)-catalyzed coupling of benzamides with propargyl alcohols via hydroarylation-lactonization process is discussed. Rh(Ⅲ)-catalyzed C-H activation and annulation of 1-benzoylpyrrolidine with propargyl alcohols has been achieved for an efficient synthesis of (4-benzylidene)isochroman-1-ones. The electrophilic amide functionality acts as an in situ functionalizable directing group. The stereochemisty of the propargyl alcohol is retained in the reactions to form highly enantio-enriched lactones.2. Umpolung of arenes that leads to C-H funcvtiponalization is presented. Using an umplolung strategy, with the assistance of the rhodium catalyst and a hypervalent iodine oxidant, the formation of a diaryliodonium salt offers an important strategy to convert the nucleophilic aryl group to an electrophilicv one. Rhodium-catalyzed coupling of arenes with sodium p-toluenesulfinate in the presence of a hypervalent iodine oxidant leads to sulfonylation. Mechanistic studies revealed that the reaction proceede with intitial hyperiodination of the arnenes, which is then functionalized by various nucleophiles.3. Co(Ⅲ)-Catalyzed synthesis of quinazolines via C-H activation of N-sulfinylimines is discussed. Quinazolines were synthesized for the first time via a C-H activation approach. With the N-S bond cleavage as an internal oxidant, the coupling of N-sulfinylimines with dioxazolones under redox-neutral conditions gave quinazolines. Mechanistic studies revealed that amidation occured first, and the amide intermediate cyclized to give the final product even in the absence of any catalyst.4. A redox-neutral avenue to access isoquinolines has been realized via cobalt-catalyzed C-H activation. Starting from readily available N-sulfinyl imine substrates and alkynes, the annulation reaction proceeded via N-S cleavage with broad substrate scope and functional group compatibility in the presence of cost-effective cobalt catalysts.