Expanding Organoboron Chemistry:  Epoxidation of Potassium Organotrifluoroborates

Most organoboron reagents are highly susceptible to oxidation by a variety of oxidants. In these processes, the valuable carbon-boron bond is cleaved. The organotrifluoroborates examined in this contribution appear resistant to many common oxidants. Consequently, thioether-substituted alkyltrifluoroborates can be oxidized to the corresponding sulfones, while retaining the trifluoroborate moiety. 1-Trifluoroboratoalkenes are oxidized by dioxirane, providing air-stable, crystalline oxiranyltrifluoroborates. These interesting materials are structurally analogous to oxiranyl anions, unstable intermediates that would otherwise be of tremendous synthetic utility. Finally, the first Suzuki-Miyaura coupling of an epoxytrifluoroborate has been accomplished. The chemistry described begins to expand organoboron chemistry in significant new directions.