Rhodium- and iridium-catalyzed oxidative coupling of benzoic acids with alkynes via regioselective C-H bond cleavage

The oxidative coupling of benzoic acids with internal alkynes effectively proceeds in the presence of [Cp*RhCl2](2) and Cu(OAc)(2)center dot H2O as catalyst and oxidant, respectively, to produce the corresponding isocoumarin derivatives. The copper salt can be reduced to a catalytic quantity under air. Interestingly, by using [Cp*IrCl2](2) in place of [Cp*RhCl2](2), the substrates undergo 1:2 coupling accompanied by decarboxylation to afford naphthalene derivatives exclusively. In this case, Ag2CO3 acts as an effective oxidant.