Divergent Three-Component Assembly of Densely Functionalized Dibenzofurans via ZnCl2-Mediated Cascade Annulation.

A ZnCl2-promoted three-component cascade ring closure of o-hydroxyphenyl propargylamines, pyridinium 1,4-zwitterionic thiolates, and nitroalkanes has been established for the rapid assembly of densely functionalized, non-symmetric tricyclic dibenzofuran frameworks. This step-economical strategy simultaneously constructs the central furan core, peripheral arene moiety, and two ester groups in a single operation. Notably, the reaction proceeds smoothly under ambient air conditions and employs undried nitroalkanes as both a C1 synthon and solvent. The protocol features mild conditions, a broad substrate scope, and excellent functional group compatibility. Moreover, its operational simplicity, scalability, and suitability for late-stage diversification underscore the synthetic utility of this methodology for complex molecular construction.