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Abstract

A direct β-arylation reaction of simple ketones with aryl iodides is developed by merging palladium-catalyzed ketone dehydrogenation, aryl-halide activation, and conjugate addition into a single catalytic cycle. Simple cyclic ketones with different ring-sizes, as well as acyclic ketones, can be directly arylated at the β-position with complete site-selectivity and excellent functional group tolerance. In addition, the β-arylation of simple ketones was also achieved using diaryliodonium salts as the aryl source. The analysis of the redox property of the reaction indicated the β-arylation reaction does not require additional oxidant or reductant, and thus redox-neutral. The new reaction tolerates both air and moisture showing a broad substrate scope for both the ketone and aryl groups. Further exploration and improvement of the β-arylation reaction were also executed. Preliminary results regarding reaction discovery and mechanistic studies were discussed. In addition, a new hydrazone-based exo-directing group strategy is devised for the functionalization of unactivated β-C–H bonds of aliphatic amines. Protected primary amines can be readily converted to hydrazone substrates via a sequence of electrophilic amination and condensation with aldehydes. The hydrazone directing groups are shown to site-selectively promote the β-acetoxylation and -tosyloxylation via 5-membered exo-palladacycles. Amines with a wide scope of skeletons, including several pharmaceuticals, as well as a large collection of functional groups are tolerated. Moreover, the hydrazone directing groups can be readily removed, and a one-pot C–H acetoxylation/directing group removal protocol was also discovered.

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