Zwitterion‐Initiated Hydroboration of Alkynes and Styrene

The hydroboration of alkynes and styrene with HBpin has been developed using tris(pentaflurophenyl)borane (B(C 6 F 5 ) 3 ) as the initiator of catalysis. The hydroboration is proposed to be initiated by Lewis acid activation of the alkyne by (B(C 6 F 5 ) 3 ) to form a highly reactive zwitterionic species which subsequently react with HBpin to give the alkenyl boronic ester. This zwitterion has also showed potential to be a competent catalyst for the hydroboration of styrene. The zwitterionic intermediate is analogous to that proposed in the Piers borane‐catalysed hydroboration and 1,1‐carboboration of alkynes with B(C 6 F 5 ) 3.