Application of Hydrogen Storage Alloy to Remove Protecting Groups.

Abstract

Hydrogen storage alloys are capable of charging and discharging hydrogen in temperature-dependent manner, and are employed as catalysts for hydrogenation and dehydration. In water, CaNi5 removed protecting groups such as benzyloxycarbonyl, benzyl ester, benzyl ether and nitro groups without any side reactions, and the reaction time was highly dependent on the hydrogen pressure of the reaction system In organic solvents such as dioxane and EtOAc the deprotection reaction did not proceed. Methanol (MeOH) was applicable, but the reaction in MeOH required a longer reaction time than in water. A mixture of water and MeOH accelerated the reaction depending on the water content. Although the mechanism of the catalytic hydrogenation with CaNi5 in water and/or MeOH is uncertain, the reaction between Ca and water or MeOH seems to be of critical importance.