(Z)- or (E)-selective hydrogenation of potassium (3,3,3-trifluoroprop-1-yn-1-yl)trifluoroborate: Route to either isomer of β-trifluoromethylstyrenes

Article abstract of DOI:10.1021/acs.orglett.5b00235

A Pd-catalyzed hydrogenation of potassium (3,3,3-trifluoroprop-1-yn-1-yl)trifluoroborate providing either the (Z)- or (E)-isomer of the vinylborate in >98% purity is described. The initially formed (Z)-isomer of the alkene is transformed to the (E)-isomer with time, irrespective of the catalyst used; coupling with bromo- and iodoarenes provides a variety of (Z)- or (E)-β-trifluoromethylstyrenes. Also, a safe synthesis of the alkynyltrifluoroborate from HFC-245fa and BF₃·OEt₂ has been described.