Selective Debenzylation in the Presence of Aromatic Chlorine on Pd/C Catalysts Effects of Catalyst Types and Reaction Kinetics

摘要

Reductive debenzylation has been widely used in the fine chemical and pharmaceutical industries. When an aromatic halogen is present, selective debenzylation verses dehalogenation has been a challenging task. In our earlier studies, transfer hydrogenolysis under different solvent, pH and salt conditions was investigated. For gaseous hydrogenolysis, a variety of palladium catalysts with different metal loadings, oxidation states and support materials were evaluated. A newly developed DeLinkIM 10%Pd/CPS4 catalyst had the desired selectivity to convert (S) to product (A) in this reaction. In contrast, the low metal loading 3%Pd/C (Engelhard nonstandard catalyst) readily over-hydrogenated the debenzylated product (A), generating the dechlorinated byproduct (B).