Regio-divergent hydroboration of terminal allenes controlled by nickel and cobalt catalysts†
A highly efficient regioselective method for allene hydroboration has been developed, with the regioselectivity governed primarily by the appropriate choice of the metal. Boryl addition to internal or external carbon–carbon bonds of the allene unit was achieved when nickel and cobalt bearing easily available phosphorus ligands were respectively employed. The complementary methods allow either regioisomeric products to be obtained with exceptional regiocontrol. It is worth mentioning that the nickel catalyst is for the first time reported to be used in allene hydroboration.