Enabling the rearrangement of unactivated allenes to 1,3-dienes by use of a palladium (0)/boric acid system

A redox neutral rearrangement of an allene to a 1,3-diene by means of a unique palladium hydride complex is reported. The palladium hydride complex is generated from a simple Pd0 source and boric acid (B(OH)3), which is typically identified as a waste by-product of the Suzuki-Miyaura reaction. A mechanism for this transformation, using this novel palladium hydride complex is presented; and using direct sample loop and flow injection ESI-HR-MS analysis we have detected and identified key π-allylpalladium complexes, that support the addition of the palladium hydride complex to the allene.