Reported herein is a novel palladium-catalyzed [2 + 2 + 1] domino annulation of 3-iodochromones, bridged olefins, and dimethyl squarate allowing the construction of chromonecontaining polycyclic compounds in good to high yields. Importantly, dimethyl squarate is first employed as the solid C1 source in organic synthesis. Gram-scale experiments, late-stage modification of natural products, as well as transformations of products show potential for further synthetic elaborations.

A variety of chromone-containing polycyclic compounds are efficiently generated via Pd-catalyzed decarboxylation [2 + 2 + 2] annulation of 3-iodochromones, bridged olefins and o-bromobenzoic acids, in which o-bromobenzoic acids were employed as the electrophilic aryl units.