Palladium-Catalyzed Oxidative [2 + 2 + 1] Annulation of 1,7-Diynes with H2O: Entry to Furo[3,4- c]quinolin-4(5 H)-ones.

A novel cascade annulation of 1,7-diynes with water has been developed for the synthesis of furo[3,4- c]quinolin-4(5 H)-one skeletons with high atom- and step-economy. The transformation was enabled by a palladium catalyst in the presence of copper salt as the promoter, involving the formation of one C-C bond and two C-O bonds. Moreover, the reaction exhibits good tolerance of functional groups and broad substrate scope. Notably, the control experiments support the incorporation of the new oxygen atom from water.