Selective Protection of Carbonyl Groups by Taking Advantage of a Combination of Solid Support and Girard’s Reagent

Some Girard’s derivatives of 4-phenylbenzophenone were prepared in ethanol solution, in the presence of Amberlite IRC-50 as a catalyst. Supported samples of the derivatives were then prepared by addition of silica gel to the solution, followed by evaporation of the ethanol. The supported samples were reduced with lithium tri-t-butoxyhydroaluminate by being suspended in THF solution. Hydrolysis, followed by extraction of the product, yielded 4-acetyl-α-phenylbenzyl alcohol in an 80% selectivity. In the same way, 4-acetylbenzaldehyde yielded 1-(4-formylphenyl)ethanol in an 81% selectivity. Relatively unhindered carbonyl groups were preferentially protected. Utilization of Girard’s reagents was successfully made as a protecting reagent and also as an extracting reagent of carbonyl compounds.