Ru-Catalyzed Selective C-H Bond Hydroxylation of Cyclic Imides.

We report on cyclic imides as weak directing groups for selective monohydroxylation reactions using ruthenium catalysis. Whereas acyclic amides are known to promote the hydroxylation of the C(sp)-H bond enabling five-membered ring ruthenacycle intermediates, the cyclic imides studied herein enabled the hydroxylation of the C(sp)-H bond via larger six-membered ruthenacycle intermediates. Furthermore, monohydroxylated products were exclusively obtained (even in the presence of overstoichiometric amounts of reagents), which was rationalized by the difficulty to accommodate coplanar intermediates once the first hydroxyl group was introduced into the substrate. The same reactivity was observed in the presence of palladium catalysts.