Access to indenofluorene skeletons via Pd-catalyzed sequential reaction involving cyclization of indenone–allenyne intermediates

We report a new method for the synthesis of polycyclic molecules of 7,12-dihydroindeno[1,2- a ]fluorene skeletons from 1-(2-iodophenyl)-3-arylprop-2-yn-1-ones and diynylic ethers via a tandem palladium-catalyzed cross-coupling, Alder–ene isomerization and cyclization sequence. Combined experimental and calculational mechanism studies suggest that the reaction proceeds via the generation and cyclization of an indenone–allenyne intermediate.