Radical-polar crossover reactions of vinylboron ate complexes
Vinyl boronic esters are valuable substrates for Suzuki-Miyaura cross-coupling reactions. However, boron-substituted alkenes have drawn little attention as radical acceptors, and the radical chemistry of vinylboron ate complexes is underexplored. We show here that carbon radicals add efficiently to vinylboron ate complexes and that their adduct radical anions undergo radical-polar crossover: A 1,2-alkyl/aryl shift from boron to the α-carbon sp2 center provides secondary or tertiary alkyl boronic esters. In contrast to the Suzuki-Miyaura coupling, a transition metal is not required, and two carbon-carbon bonds are formed. The valuable boronic ester moiety remains in the product and can be used in follow-up chemistry, enlarging the chemical space of the method. The cascade uses commercial starting materials and provides access to perfluoroalkylated alcohols, γ-lactones, γ-hydroxy alkylnitriles, and compounds bearing quaternary carbon centers.