Transition-metal-free synthesis of (Z)-3-ylidenephthalides from 2-acyl-benzoic acids

We report a highly efficient method for the synthesis of (Z)-3-ylidenephthalides via intramolecular cyclization of readily available 2-acyl-benzoic acids mediated by TSTU at room temperature. Using this method, diversely substituted (Z)-3-ylidenephthalides have been generated in good to excellent yields. The application of the method is highlighted by gram-scale preparation of the antiplatelet drug n-butylphthalide.