Catalytic Carbo- and Aminoboration of Alkenyl Carbonyl Compounds via Five- and Six-Membered Palladacycles

A palladium(II)-catalyzed alkene difunctionalization reaction has been developed, wherein B(2)pin(2) is used to trap chelation-stabilized alkylpalladium(II) intermediates that are formed upon nucleopalladation. A range of carbon and nitrogen nucleophiles were found to be suitable coupling partners in this transformation, providing moderate to high yields. Both 3-butenoic and 4-pentenoic acid derivatives were reactive substrate classes, affording beta,gamma- and gamma,delta-difunctionalized carboxylic acid derivatives. This work represents a new strategy to synthesize highly functionalized secondary boronates that complements existing methods.