Oxygen Bonded to Activated Tetrahedral Carbon Atoms

Oxygen Bonded to Activated Tetrahedral Carbon Atoms 

Acetals Removing the acetal protecting group is easily achieved by acid-catalyzed hydrolysis, although catalytic hydrogenolysis is better for acid-sensitive compounds. The oxygen connected to the 

and Rh the regioselectivity depends on the conditions. Mainly ester is formed at low hydrogen pressures, whereas mainly diol monoether is formed at higher pressures.30 31 Selectivity is structure-sensitive more ester is formed on highly dispersed catalysts. 

Benzyl and Allyl Carbon Atoms Hydrogenolysis of a carbon-heteroatom bond is extremely fast if the heteroatom is connected to allylic or benzylic carbon atoms. The benzylic compounds are used very frequently in organic chemistry as protecting groups. Because of its great importance the benzylic compounds are discussed separately in the next section. 

In some cases it is necessary to hydrogenate allylic compounds to saturated molecules without hydrogenolysis. It was found that nickel boride is a good catalyst for this purpose.46 

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