Palladium-Catalyzed Difunctionalization of Norbornenes via Arylation and Alkynylation.

We report the first general and practical method for the addition of aryl halides and alkynes to norbornenes with palladium catalysis. Norbornenes have been used as the unsaturated acceptors of aryl and alkynyl groups to construct saturated bridged C-C bonds. The combination of Pd(OAc) 2 /PCy 3 HBF 4 has been identified as the optimal system promoting difunctionalization of norbornenes via the C-X/C-H bond cleavage and highly selective C(sp 3 )-C(sp 2 )/C(sp 3 )-C(sp) bond formation. Broad substrate scope and excellent functional group tolerance have been achieved to show the high efficiency of this approach. Mechanism studies based on experiments and DFT have been performed to gain insights into the catalytic mechanism.