Mild and efficient construction of nitrogen-containing heterocycles from ortho-ethynylbenzaldehydes and anilines

Abstract

A mild and transition-metal-free strategy for the synthesis of isoindolin-1-imines and isoquinolinium salts has been developed using ortho-ethynylbenzaldehydes and anilines. HFIP was employed as an effective promoter, facilitating nucleophilic addition and annulation to afford diverse isoindolin-1-imines in good yields. Alternatively, isoquinolinium salts were obtained by addition of ammonium iodide. Both reactions exhibited broad functional group tolerance and were successfully applied on gram scales as well as for further transformation, providing a practical strategy in pharmaceutical development and organic synthesis.