No abstract

Herein we report a highly para-selective C–H olefination of aniline derivatives by a Pd/S,O-ligand-based catalyst. The reaction proceeds under mild reaction conditions with high efficiency and broad substrate scope, including mono-, di-, and trisubstituted tertiary, secondary, and primary anilines. The S,O-ligand is responsible for the dramatic improvements in substrate scope and the high para-selectivity observed. This methodology is operationally simple, scalable, and can be performed under aerobic conditions.

Pd(II)-catalyzed C–H functionalization of nondirected arenes has been realized using an inexpensive and easily accessible type of bidentate S,O-ligand. The catalytic system shows high efficiency in the C–H olefination reaction of electron-rich and electron-poor arenes. This methodology is operationally simple, scalable, and can be used in late-stage functionalization of complex molecules. The broad applicability of this catalyst has been showcased in other transformations such as Pd(II)-catalyzed C–H acetoxylation and allylation reactions.

Reversing the conventional site-selectivity of CÀ H activation processes provides new retrosynthetic disconnections to otherwise unreactive bonds. Here, we report a new catalytic system based on palladium/ norbornene and an S,O-ligand for the meta-CÀ H arylation of aryl ethers that significantly outperforms previously reported systems. We demonstrate the unique ability of this system to employ alkoxyarene substrates bearing electron donating and withdrawing substituents. Additionally, ortho-substituted aryl ethers are well tolerated, overcoming the "ortho constraint", which is the necessity to have a meta-substituent on the alkoxyarene to achieve high reaction efficiency, by enlisting novel norbornene mediators. Remarkably, for the first time the monoarylation of alkoxyarenes is achieved efficiently enabling the subsequent introduction of a second, different aryl coupling partner to rapidly furnish unsymmetrical terphenyls. Further insight into the reaction mechanism was achieved by isolation and characterization of some Pd-complexesbefore and after meta CÀ H activation-prior to evaluation of their respective catalytic activities.