Iodomethane in C1 chemistry: application in palladium-catalyzed [2 + 2 + 1] annulation

An efficient palladium-catalyzed [2 + 2 + 1] annulation of 3-iodochromones, bridged olefins, and iodomethane is described, affording a range of chromone-containing polycyclic compounds. Additionally, the corresponding deuterated products were smoothly obtained with iodomethane- d 3 instead of iodomethane. Moreover, the synthetic utility of this method is further substantiated by gram scale preparation and application to late-stage modification of estrone. A variety of chromone-containing polycyclic compounds were smoothly forged in up to 93% yield via palladium-catalyzed [2 + 2 + 1] annulation of 3-iodochromones, bridged olefins, and iodomethane, in which iodomethane was used as the methylene source.