Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions

Abstract

An efficient and practical arene hydrogenation procedure based on the use of heterogeneous platinum group catalysts has been developed. Rh/C is the most effective catalyst for the hydrogenation of the aromatic ring, which can be conducted in iPrOH under neutral conditions and at ordinary to medium H(2) pressures (<10 atm). A variety of arenes such as alkylbenzenes, benzoic acids, pyridines, furans, are hydrogenated to the corresponding cyclohexyl and heterocyclic compounds in good to excellent yields. The use of Ru/C, less expensive than Rh/C, affords an effective and practical method for the hydrogenation of arenes including phenols. Both catalysts can be reused several times after simple filtration without any significant loss of catalytic activity.

The quest for odorants having salicylate notes

“…The main drawback is that the Fries rearrangement is usually not selective and leads, in the case where the para position of the phenol is unsubstituted, to a mixture of ortho and para products, even if authors have sometimes claimed good selectivities, depending on the conditions used (Scheme ). The ratio seems mainly dependent on the temperature, as well as on the nature and amount of Lewis acid used …”

Ruthenium Nanoparticles Stabilized in Cross‐Linked Dendrimer Matrices: Hydrogenation of Phenols in Aqueous Media

“…As a rule, the catalysts used are those in which the metal is deposited onto a heterogeneous carrier (i.e., silica,5 alumina,6 or carbon7). It has been shown that ruthenium systems are preferable for the hydrogenation of phenols of various structures 7a. Thus, the Ru/C catalyst at temperatures of 60–120 °C and hydrogen pressures of 5–10 atm gives 90–100 % conversions for a wide range of substrates.…”

Facile Arene Hydrogenation under Flow Conditions Catalyzed by Rhodium or Ruthenium on Carbon

“…In our laboratory, 10 % rhodium on carbon (Rh/ C) and 10 % ruthenium on carbon (Ru/C), both of which are reusable, were found to be very effective catalysts for the hydrogenation of aromatic rings to afford a variety of saturated cyclic compounds in excellent yields under mild conditions (e.g., 1 atm, 60°C). [4] Continuous-flow hydrogenation reactions with gaseous hydrogen and a solid catalyst, the latter of which is packed in a cartridge inserted into the flow path of the substrate solution, have drawn significant attention owing to the easy handling and safety of such technology; for example, the catalysts can be continuously reused a number of times without replacement, the metal contamination into the 1 10 % rhodium on carbon (Rh/C) or 10 % ruthenium on carbon (Ru/C) under neutral conditions. The protocol was successfully applied to a 10 mmol scale reaction.…”