Ruthenium(II)-Catalyzed C@H Difluoromethylation of Ketoximes: Tuning the Regioselectivity from the meta to the para Position
Chunchen Yuan1,+, Lei Zhu2,+, Runsheng Zeng1, Yu Lan2,*（蓝宇）, and Yingsheng Zhao1,*（赵应声）
1Key Laboratory of Organic Synthesis of Jiangsu Province
College of Chemistry, Chemical Engineering, and Materials Science
Soochow University,Suzhou 215123 (P.R. China)
2School of Chemistry and Chemical Engineering,Chongqing University,
Chongqing 40030 (P.R. China)
[+]These authors contributed equally.
Angew. Chem. Int. Ed.2018,57, 1277--1281
A highlypara‐selective CAr−H difluoromethylation of ketoxime ethers under ruthenium catalysis has been developed. A wide variety of ketoxime ethers are compatible with the reaction, which leads to the correspondingpara‐difluoromethylated products in moderate to good yield. A mechanistic study clearly showed that chelation‐assisted cycloruthenation is the key factor in theparaselectivity of the difluoromethylation of ketoxime ethers. Density functional theory was used to gain a theoretical understanding of theparaselectivity.