One-pot stepwise and consecutive mechanistically incompatible solvent-free reactions: Synthetic and mechanistic insights

Pd nanoparticles supported on an accessible laponite clay are efficient and highly recoverable catalytic systems in benchmark coupling and hydrogenation reactions under solvent-free conditions. In this paper, we explore the use of these supported catalytic systems in one-pot stepwise and consecutive reactions with excellent isolated yields. Whereas the catalyst recovered from hydrogenation reactions remains active in both coupling and hydrogenation processes, the catalyst used in coupling reactions is progressively deactivated for further hydrogenations. This behavior is not due neither to the nanoparticles agglomeration nor to Pd leaching, but to the formation of Pd(II) on the catalyst surface, disclosing a clear XPS evidence for the theory of the “release and capture” mechanism. Nonetheless, the hydrogenation activity is fully recovered after reducing this surface Pd(II) using ethanol. Finally, we have applied this strategy in the synthesis of products with practical pharmaceutical interest such as nabumetone and resveratrol.