Modular access to furo[3,2-]chromen-4-ones Yb(OTf)-catalyzed [3 + 2] annulation of 4-hydroxycoumarins with β-nitroalkenes.

A facile and efficient strategy for modular access to furo[3,2-]chromen-4-ones using 4-hydroxycoumarin and β-nitroalkenes Lewis acid-catalyzed formal [3 + 2] annulation protocol is described. This reaction proceeds cascade Michael addition/nucleophilic addition/elimination in the presence of Yb(OTf), which involves the formation of two new σ (C-C and C-O) bonds for the construction of a novel furan ring in a single operation. This protocol affords a variety of functional groups, thereby providing a practical and efficient method for the fabrication of a furo[3,2-]chromen-4-one framework.