The Discovery of a Palladium(II)-Initiated Borono-Catellani Reaction.

Reported is a novel palladium(II)-initiated Catellani-type reaction that utilizes widely accessible aryl boronic acids as the substrates instead of aryl halides, thereby greatly expanding the existing scope of this powerful transformation. This borono-Catellani reaction was promoted by cooperative catalysis between Pd(OAc)2 and the inexpensive 5-norbornene-2-carbonitrile. Practicality is the striking feature of the reaction: it is run open to air at ambient temperature and no phosphine ligand is needed. This mild, chemoselective, and scalable protocol is compatible with a large range of readily available functionalized aryl boronic acids and bromides, as well as terminating olefins (50 examples, 39-97 % yields). Moreover, the orthogonal reactivity between the borono-Catellani and classical Catellani reaction was demonstrated. This work is expected to open new avenues for developing novel Catellani-type reactions.