Ruthenium(II)-catalyzed C-H activation/lactonization of aromatic acids with diazonaphthoquinones: regioselective synthesis of polycyclic coumarin frameworks

A straightforward synthesis of biologically relevant dibenzo[c,h]chromen-6-one and dibenzo[c,f]chromen-5-one frameworks has been accomplished by leveraging a one-pot annulative coupling of aromatic acids with diazonaphthoquinones under ruthenium catalysis. The protocol harnessed the assistance of weak coordination and displayed high reaction yields with broad functional group tolerance, scalability, and scaffold diversity. This annulation was also fruitful in the presence of diverse pharmacophore scaffolds including commercial drugs. The reaction involved a reversible C-H metalation step and a ruthenium(IV)-containing intermediate.