Studies Of Transition Metal-Catalyzed Oxidative Functionalization Of Sp~3C-H Bonds Adjacent To Heteroatoms

Transition metal-catalyzed C-H activation has recently emerged as the most powerful and straightforward tool for the functionalization of organic molecules. Although many efforts have focused on the direct sp2C-H activation in the past two decades, much less research has been devoted to the activation of more inert sp3C-H bonds. In this dissertation, we investigated transition metal-catalyzed oxidative functionalization of sp3C-H bonds. The contents were listed as below:1. CuBr-Catalyzed Reaction of N,N-Dimethylanilines with Silyl Enol EthersA wide range of silyl enol ethers undergo the reactions with N,N-dimethylanilines in the presence of transition metal-catalysts under mild conditions to give β-arylamino ketones. In the cases of silyl enol ethers derived from unsymmetrical ketones, regiospecific addition of carbonyl compounds was obtained at the olefinic position of silyl enol ethers. In addition, enol ethers also undergo the reactions with N,N-dimethylanilines to afford the derivatives of quinonlines via the intramolecular annulation in a single step. This method provided a convenient alternative for synthesis of β-arylamino ketones, which were difficult to be prepared by traditional Mannich reaction or aza-Micheal addition reaction.2. Copper-Catalyzed Oxidative Cross-Coupling of N,N-Dimethylanilines with HeteroarenesA direct cross-coupling reaction of N-heterocyclic sp2C-H bonds with sp3C-H bonds of anilines in the presence of copper catalyst was developed using molecular oxygen or air as the oxidant. The reaction was compatible with a wide range of N-heterocycles, including indolizines, imidazoles, indoles and aniline, to afford various alkylated N-heteroarenes under very mild reaction conditions. When indole was used as the substrate, not only the desired cross-coupling products were formed, but also the N-alkylated products were isolated. In addition, indolizine coupling products with N,N-dimethylbenzenamine in the presence of10mol%anhydrous to give the valuable benzylic indolizines in good yields. A quite efficient sp2C-H and sp3C-H cross-coupling reaction was developed: treatment of two unfunctionalized substrates with5mol%CuBr in stirring at50℃in air generated the cross-coupling product, the article is one of the Top10most read articles in Q12011from J. Org. Chem.3. Copper-Catalyzed Addition of sp3C-H Bonds Across Carbon-Carbon Triple BondsCopper-catalyzed addition of sp C-H bond in tetrahydrofuran adjacent to oxygen atom into alkynes has been realized regioselectively under mild conditions in the presence of tert-butyl hydroperoxide (TBHP) to give the alkenylated products. The terminal arylalkynes with both electron-donating and electron-withdrawing substitutents in the aryl ring gave the corresponding products in moderate to good yields. The reaction also tolerated the halide substituents, which were useful for further functionalization. We also studied the reaction of1,3-dioxolane, in which there are two kinds of C-H bonds next to oxygen. The selectivity toward the C-H bond activation at2-position was examined and the2-alkenylated1,3-dioxolanes were delivered as the major products. The reaction provided a convenient method for β-alkylated alkenes by addition of sp3C-H bond next to a oxygen atom under mild conditions.4. Iron-Promoted C-C Bond Cleavage of1,3-Diketones to1,2-DiketonesAn iron-promoted method for the synthesis of1,2-diketones through the selective C-C bond cleavage of1,3-diketones under mild reaction conditions in air was developed by the use of tert-butyl nitrite (TBN) as the oxidant without the use of solvent. A variety of symmetrical and unsymmetrical (hetero)aromatic1,3-diketones gave the corresponding products in high yields. The possible reaction mechanism was discussed. This protocol provided an expeditious route to the useful1,2-diketones.