Hydrogenolysis of Benzyl Groups Attached to Oxygen, Nitrogen, or Sulfur

Abstract

The benzyl group and a variety of substituted benzyl groups attached to an oxygen atom as in alcohols, ethers, acetals, or esters; to an amino nitrogen atom; or to a sulfur atom in thio ethers may be removed as toluene, or the corresponding substituted toluene, by hydrogenolysis. Other chemical and catalytic methods have been employed to bring about these debenzylations. It is the purpose of this chapter to give illustrations of both types of debenzylations so that their usefulness may be appreciated.

Synthesis and enzymatic evaluation of ketose phosphonates: the interplay between mutarotation, monofluorination and acidity

“…Treatment of 13 with m-CPBA 55 in CH 2 Cl 2 followed by aqueous work up introduced a 1,2-diol functionality at the a,bposition to the phosphorus in compound 17. Keto-phosphonates 12, 15, 16, and 17 were deprotected efficiently by a two-step procedure starting with hydrogenolysis (Pd/C) 56,57 either under atmospheric pressure or in a Parr shaker at 50 psi in a solvent system of 1 : 1 MeOH/EtOAc. Neutralization of the resulting phosphonic acid derivatives with aqueous NH 4 OH solution gave the final phosphonates 3, 4, 5, and 7, respectively, in yields ranging from 78-82% over two steps.…”

Can Heteroarenes/Arenes Be Hydrogenated Over Catalytic Pd/C Under Ambient Conditions?

“…Palladium catalyst on activated carbon (Pd/C) has been widely used for the hydrogenative reduction of olefin, alkyne, nitro, nitrile, N ‐oxide, benzylic carbonyl, or hydroxyl groups as well as hydrogenolytic deprotection of N/O/S ‐benzyl groups due to its commercial availability and suitability for experimental applications. Hydrogenation of 4‐pyridinecarboxamides over Pd/C in the presence of 1,2‐dichloroethane has been achieved .…”

Removal of benzylidene acetal and benzyl ether in carbohydrate derivatives using triethylsilane and Pd/C

“…A number of methods have been reported for the removal of benzylidene acetals by using strong protic and Lewis acids [10–11 15] as well as some heterogeneous acidic catalysts [16–17]. Removal of benzylidene acetal under nonacidic conditions includes hydrogenolysis using hydrogen gas over Pd/C [18], or treatment with hydrazine [19] or EtSH [20] or Na/NH 3 [21], etc. However, most of the above-mentioned methodologies have several shortcomings, such as harsh conditions, formation of unwanted byproducts, longer reaction time, incompatibility of functional groups, use of expensive reagents, fire hazard, etc.…”