Transition-metal Promoted C-H Activation Of Aniline Derivatives

Metallic-reagents oriented organic synthesis and green chemistry are two important topics in organic chemistry. Following these topics, this dissertation studied the transition-metal promoted C-H activation of N,N-dialkylanilines and C-C/C-N bond formation. The research work included three parts. Part I: Cerium salts promoted oxidative homo-coupling reactions of N,N-dialkylanilines; Part II: Synthesis of tetrahydroquinoline derivatives from N-methylalkylanilines from a solvent-free catalytic reaction in one-pot; Part III: High-efficient nitration reaction of N,N-dialkylanilines under mild and neutral conditions.Part I: Benzidine derivatives have great potential application in the field of photo-electric material. The most atom-economy method to form benzidine derivatives was oxidative coupling of N,N-dialkylanilines via C-H activation. Based on the cerium ammonium nitrate (CAN) induced oxidative coupling of N,N-dialkylanilines in aqueous media, we further studied the efficiency of other ceric salts under the same condition and developed a Ce(IV) promoted oxidative coupling of N,N-dialkylanilines in solid state. Additionally, the cerium salts catalyzed oxidative coupling reaction was also carried out, with H₂O₂ as the oxidant to promote the cyclization between Ce(IV) and Ce(III).Part II: Tetrahydroquinoline skeleton is an important structure unit in natural products. The traditional synthesis of such derivatives usually need rigorous condition or multiple steps, or directly from hydrogenation of quinolines. We found a new method to form tetrahydroquinoline derivatives via C-H activation of N-methylalkylanilines, which was a one-pot formation of 1,4-disubstituted tetrahydroquinolines by cross-coupling between N-methylalkylanilines and alkyl vinyl ethers with CuCl+2 as the catalyst and excess of tertbutylhyperoxide (TBHP) as the oxidant. This reaction, which contained two C-H bonds cleavage and two C-C bonds formation, was highly atom-economy and can be carried out open-to-air without any solvent. Part III: Nitro-aromatic compounds are broadly applied in many industrial fields, but the conventional methods to synthesis such products always need strong acidic condition with unsatisfying yield and/or selectivity. In the course of studying the C-H activation of N,N-dialkylanilines, we discovered two Ce(IV)-induced nitration reactions: 1) Highly regio-selective nitration of N,N-dialkylanilines in CAN-acetonitrile solution, and 2) Nitration of N,N-dialkylanilines in an aqueous solution of Ce (IV) salts and sodium nitrite.