Syntheses of Benzo[c]Chromen-6-ones by Palladium Catalyzed C-H Bond Activation using Diazonium Salts

An efficient palladium catalyzed C-H bond activation for the synthesis of benzo[c]chromen-6-ones using diazonium salts is described. In the presence of Pd(OAc)(2), dppp, PivOH and K2CO3, the diazonium salt can be transformed into the product through a denitrogenation/C-H bond activation/cyclization sequence in acetonitrile. Altogether, nine structurally diverse substituted benzo[c]chromen-6-ones were prepared in excellent yields through two different methods.