An efficient potassium carbonate-catalyzed synthesis of 3-substituted isoindolinones through tandem aldol/cyclization reactions of active methylene compounds with 2-cyanobenzaldehyde is described. The utility of the obtained isoindolinones has been demonstrated through an exploration of the chemical space by employing a series of interesting methodologies that led to diverse, highly functionalized compounds. Among them, a surprisingly straightforward potassiumcarbonate-catalyzed double tandem reaction led to tricyclic hemiaminal derivatives.