An expeditious FeCl 3 -catalyzed cascade 1,4-conjugate addition/annulation/1,5-H shift sequence for modular access of all-pyrano-moiety-substituted chromenes.

ortho -Alkynyl quinone methides are well-known four-atom synthons for direct [4 + n ] cycloaddition in constructing useful oxa-heterocyclic compounds owing to their high reactivity as well as the thermodynamically favored aromatization nature of this process. Herein we report an operationally simple and eco-friendly protocol for the modular and regioselective access of ( E )-4-(vinyl or aryl or alkynyl)iminochromenes from propargylamines and S -methylated β-ketothioamides in the presence of FeCl 3 , and particularly under undried acetonitrile and air atmosphere conditions. This method exhibits a broad substrate scope and displays nice functional group compatibility, thus providing an efficient access of 3,4-disubstituted iminochromenes.