Catalytic hydrogenations of cyclic imides and ayhydrides

Abstract

The carbonyI functions in phthalimide and succinimide are unaffected on attempted hydrogenation in ethyl acetate at room temperature and atmospheric pressure over platnum oxide catalyst. Hydrogenation in the imide ring in these compounds can be accomplished under such conditions if an acetyl or other acyl group is attached to the imide nitrogen atom. An important alternative reaction, competitive hydrogenolytic cleavage of the acyl group, can be eliminakte by using an alkoxycarbonyl sunstiktuent. The sterochemistry of the products obtained from N-acylphthalimides and varying the nature of the acyl substituent on reaction rate and product composition have been determined. On the basis of these and previously reported results on the hydrogenation of a series of cyclic anhydrides under similar conditions a mechanism is proposed for the hydrogenation of cyclic imides and anhydrides.

The catalytic hydrogenation of certain N-acylphthalimides, in ethyl acetate or ethanol at room temperature and atmospheric pressure over 10% palladium on carbon catalyst, gives the corresponding 2-acyl-3-hydroxydihydroisoindol-1-ones in high yield.