Synthesis of 3-arylphthalides with a quaternary carbon center via [4+1] cycloaddition of 2-carbonylcyclohexadienimines with isocyanides under metal-free conditions

Rapid synthesis of 3-arylphthalides with a quaternary carbon center has been achieved via a cascade [4+1] cycloaddition/nucleophilic 1,4-addition of 2-carbonylcyclohexadienimines with two molecules of isocyanides. The reaction proceeded smoothly under metal-free conditions leading to the formation of multi-functionalized phthalides in moderate to good yields.