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(Z)- or (E)‑Selective Hydrogenation of Potassium (3,3,3-Trifluoroprop-1-yn-1-yl)trifluoroborate: Route to Either Isomer of β‑Trifluoromethylstyrenes

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journal contribution
posted on 06.03.2015, 00:00 by P. Veeraraghavan Ramachandran, Wataru Mitsuhashi
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.