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(sp2)–H bond enabling five-membered ring ruthenacycle intermediates,
the cyclic imides studied herein enabled the hydroxylation of the
C­(sp2)–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.