Substituent Effects on Hydrogenation of Aromatic Rings: Hydrogenation vs. Hydrogenolysis in Cyclic Analogues of Benzyl Ethers.

Article abstract of DOI:10.1021/jo00212a025

Carbalkoxy substituents are shown to retard the hydrogenation of aromatic rings over Rh/C catalyst.Hydrogenolysis predominates with acyclic (benzyloxy)acetates over this catalyst, but both hydrogenation and hydrogenolysis become sluggish with 2-isochroman-4-ones (1).However, phthalides may be cleanly hydrogenated in moderate to excellent yields without significant hydrogenolysis.Placing a benzyl ether in a ring system appears to greatly retard hydrogenolysis relative to the acyclic analogues.