Characterization of Two Stable Degradants of Palladium tBuXPhos Catalyst and a Unique Dearomatization Reaction

Two stable degradants of palladium tBuXPhos catalyst have been synthesized from tBuXPhos and Pd2(dba)3·CHCl3, isolated, and fully characterized. Complex 2 augments the known literature examples of palladacycles from this ligand family but is present as a rare four-membered-ring palladacycle, having activated the top ring of the ligand. Complex 3 is an unusual case of palladium-mediated dearomatization, whereby chloroform functionalizes the bottom ring, generating a palladium allyl complex. The mechanism is assigned to an electrophilic carbene attack where palladium directs attack of dichlorocarbene to the anti face of the bottom arene. The structures have been confirmed by NMR and single-crystal X-ray diffraction.