Reduction of Benzolactams to Isoindoles via an Alkoxide-Catalyzed Hydrosilylation

An alkoxide-catalyzed reduction of benzolactams to isoindoles with silanes was realized. With t-BuOK as the catalyst and Ph₂SiH₂ as the reductant, a series of benzolactams containing different functional groups were reduced to the corresponding isoindoles, which could be captured by N-phenyl maleimide to form Diels-Alder products in moderate to good yields. Deuterium labeling studies and the hydrosilylation of benzolactam in DMF indicated that the deprotonation of benzolactams took place at C3 potion during the reduction.