Chromium-Catalyzed Selective Borylation of Vinyl Triflates and Unactivated Aryl Carboxylic Esters with Pinacolborane

The use of pinacolborane to borylate abundant vinyl triflates and unactivated aryl carboxylic esters was enabled by chromium catalysis via the selective formation of vinyl and aryl boronate esters. The competing hydrided reduction or allylic borylation proceeds sluggishly or does not occur, therefore providing a selective strategy for the incorporation of boronate into olefins and arenes. Mechanistic studies indicate that the σ-bond metathesis or oxidative addition mechanism may be considered to be responsible for the cleavage of ester scaffolds.