Rhodium/Graphite-Catalyzed Hydrogenation of Carbocyclic and Heterocyclic Aromatic Compounds

Rhodium on graphite (Rh/Gr, C(24)Rh) was prepared by reaction of anhydrous rhodium trichloride with potassium graphite (C(8)K, 3 equivalents) and used as a heterogeneous catalyst for the hydrogenation of carbocyclic and heterocyclic aromatic compounds at room temperature and 1 atm of hydrogen pressure. The effect of substitution on the benzene ring was examined in a variety of derivatives, including those with alkyl, hydroxy, alkoxy, aryloxy, carboxy, amino, nitro, acyl, chloro, or functionalized alkyl groups. Reduction of carbonyl functions of aromatic aldehydes and ketones occurred with complete or partial cleavage of the benzylic C-O bond; this cleavage also occurred in the hydrogenation of benzylic alcohols and esters.