How is Aripiprazole Impurity 31 (CAS: 19315-93-6) typically synthesized?

Aripiprazole Impurity 31 is synthesized through the reduction of 1,2-dihydro-2,6-dimethyl-3-(1,3-dioxoisoindolin-2-yl) quinoline with a hydrogenation catalyst such as palladium on carbon. The reaction typically requires high purity starting materials and is conducted in an inert atmosphere to prevent oxidation. The yield is usually around 85-90%, and the process is optimized for selectivity and purity.