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 B2pin2 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 β,γ-
and γ,δ-difunctionalized carboxylic acid derivatives.
This work represents a new strategy to synthesize highly functionalized
secondary boronates that complements existing methods.