Catalytic Hydrogenation of Conjugated Dienes With Different Reactivities Using a Pd/C Nanophase Catalyst

A Pd-C catalyst, prepared by decomposition of tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) on activated carbon (5 % Pd), was found to efficiently catalyze the hydrogenation reaction of diene carboxylates featuring isolated saturated ring scaffolds. Under 100 atm H₂ at 30 °C for 24 h in MeOH, the catalyst proposed provided significantly higher yields of the fully saturated products than other tested Pd/C catalysts, particularly for the less reactive five-membered-ring diene substrate. In contrast, hydrogenation of a more reactive six-membered diene proceeded to high conversion with all catalysts. All studied catalysts showed diminished activity in AcOH (requiring higher Pd loadings for comparable conversion), and very low yields in hexane or THF (consistent with the low H2 solubility in these solvents). We believe that the proposed Pd/C nanocomposite could be especially beneficial for the hydrogenation of low-reactivity organic compounds, especially for accessing functionalized sp³-enriched bicyclic scaffolds.