Highly stereoselective synthesis of cis-alkenyl pinacolboronates and potassium cis-alkenyltrifluoroborates via a hydroboration/protodeboronation approach

A number of alkynyl pinacolboronates bearing various functional groups were synthesized according to literature methods. These were then stereoselectively reduced to the cis-alkenyl pinacolboronates via hydroboration with dicyclohexylborane followed by chemoselective protodeboronation using acetic acid. Treatment with potassium hydrogen fluoride smoothly converted these to the corresponding potassium organotrifluoroborates.