Optimized Conditions for the Palladium‐Catalyzed Hydrogenolysis of Benzyl and Naphthylmethyl Ethers: Preventing Saturation of Aromatic Protecting Groups

While carrying out palladium‐catalyzed hydrogenolysis to deprotect synthetic oligosaccharides, saturation of the benzyl and naphthylmethyl ether groups to their corresponding ether was observed. In order to suppress this unwanted hydrogenation, we report a scalable practical approach using a catalyst pre‐treatment strategy, which is effective under batch or continuous flow conditions. This suppressed the unwanted hydrogenation side‐products and created a selective catalyst for hydrogenolysis of benzyl and naphthylmethyl ethers. We demonstrate the efficient deprotection of a set of structurally diverse oligosaccharides (5 examples, > 73 %). Tuning of a palladium catalyst reactivity allows the chemoselective removal of benzyl and naphthyl protecting groups under batch or continuous flow conditions. Hydrogenation of the aromatic groups does not occur under these conditions thus allowing access to pure synthetic glycans.