Synthesis of Benzofuro[3,2-c]isoquinolines through Anionic Intramolecular Cyclization

Abstract Benzofuro[3,2-c]isoquinolines are among the typical tetraheterocycles. The synthesis of benzofuro[3,2-c]isoquinoline derivatives in the presence of a catalytic amount of KOH has been developed. A variety of substituents could be tolerated. The base (KOH) works as a catalyst. A gram-scale synthesis was performed. Control experiments confirmed that a cascade anionic annulation is involved rather than a radical cyclization.