Expeditious Multicomponent Synthesis of Xanthone Dimers ^†

Xanthones are a type of compound widely found in many natural products from plants, fungi, and lichens and are considered privileged structures. Frequently, xanthones occur in nature as dimers, which often exhibit singular and potent biological effects. Although diverse methods for the synthesis of monomeric xanthones are known, dimeric xanthones remain synthetically challenging targets. Reported syntheses of dimeric xanthones are very scarce, and invariably involve a large number of synthetic steps. We have recently developed a multicomponent synthesis of xanthones starting from 3-carbonylchromones, isocyanides, and dienophiles. Here we report a similar one-pot tandem procedure, involving a [4+1]-[4+2] cycloaddition, that readily affords dimeric xanthones and dihydroxanthones, which are structurally similar to bioactive ergochromes.