Synthesis of Isoindole N -Oxides by Palladium-Catalyzed C-H Functionalization of Aldonitrones.

A palladium-catalyzed strategy for isoindole N -oxide ring construction by C-H functionalization of aldonitrones is described. Our protocol is of general character, providing isoindole N -oxides with a variety of functional groups, including very sterically congested products. Further transformations into spirocyclic isoindolines, isoindoles, or a polycyclic isoquinolinium salt have been demonstrated as well. A mechanistic study suggests that the catalytic process proceeds via a Heck-type addition to the double C═N bond.