Quaternary carbe | Density functional theory | Annulation | Alkynes | Synthetic methods Through the intramolecular cyclization of N-methoxybenzamides, a simple and efficient method for constructing valuable isoindolinones under metal-free conditions was developed. The reaction was featured by employing low-cost catalyst, simple operation, 100% atomic economy and excellent regioselectivity. Moreover, a detailed computational study on the reaction system has been performed to clarify the mechanism. This protocol tolerated a variety of functional groups and provided a metal-free protocol for the synthesis of chromane-or tetrahydroquinoline-fused isoindolinones in good yields.