Formation of Nucleophilic Allylboranes from Molecular Hydrogen and Allenes Catalyzed by a Pyridonate Borane that Displays Frustrated Lewis Pair Reactivity.

Here we report the in situ generation of nucleophilic allylboranes from H2 and allenes mediated by a pyridonate borane that displays frustrated-Lewis-pair reactivity. Experimental and computational mechanistic investigations reveal that upon H2 activation, the covalently bound pyridonate substituent becomes a datively bound pyridone ligand. Dissociation of the formed pyridone borane complex liberates Piers borane and enables a hydroboration of the allene. The allylboranes generated in this way are reactive towards nitriles. A catalytic protocol for the formation of allylboranes from H2 and allenes and the allylation of nitriles has been devised. This catalytic reaction is a conceptually new way to use molecular H2 in organic synthesis.