A base-mediated dearomatization [2 + 3] annulation of 2-nitrobenzofurans with 4-hydroxycoumarins: A simple and direct synthesis of dihydrofurobenzofuran-coumarins

A simple base-mediated dearomatization [2 + 3] annulation of 2-nitrobenzofurans with 4-hydroxycoumarins has been reported. A series of polycyclic heterocycles bearing dihydrofurobenzofuran and coumarin blocks were synthesized via Michael/nucleophilic substitution cascade reaction in moderate to excellent yields. 2-Nitrobenzothiophene and 4-hydroxyquinolin-2-one are also tolerated in this protocol. The reaction can be carried out on a gram scale. The configuration of product is confirmed by X-ray single crystal structure analysis.