Palladium/norbornene (Pd/NBE) cooperative catalysis, also known as the Catellani reaction, has become an increasingly useful method for site-selective arene functionalization; however, certain constraints still exist due to its intrinsic mechanistic pathway. Herein we report a redox-neutral functionalization of aryl boroxines via Pd/NBE catalysis. An electrophile, such as carboxylic acid anhydrides or -benzoyl hydroxylamines, is coupled at the boroxine position, and a proton as the second electrophile is introduced at the position. This reaction does not require extra oxidants or reductants, and avoids stoichiometric bases or acids, thereby tolerating a wide range of functional groups. In particular, orthogonal chemoselectivity between aryl iodide and boroxine moieties is demonstrated, which could be used to control reaction sequences. Finally, a deuterium labelling study supports the -protonation pathway. This unique mechanistic feature could inspire the development of a new class of Pd/NBE-catalyzed transformations.
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| http://dx.doi.org/10.1016/j.chempr.2019.02.005 | DOI Listing |
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