Rh(III)-catalyzed chemodivergent synthesis of isocoumarins and isoquinolones from <i>N</i> -methoxybenzamides and cyclic α-diazo-1,3-diketones

Abstract This letter describes the chemodivergent synthesis of isocoumarins and isoquinolones using identical starting materials. A rhodium(III) catalyst induces C(sp2)–H bond activation, carbene migratory insertion, and intramolecular annulation under mild reaction conditions. The selectivity of isocoumarins versus isoquinolones is tuned by controlling the additives. Specifically, acetic acid promotes lactonization, affording isocoumarins, whereas the cationic Cp*Rh(III) (Cp* = ƞ5-pentamethylcyclopentadienyl) facilitates lactamization, affording isoquinolones. Overall, the developed protocol enables chemodivergent synthesis of isocoumarins and isoquinolones with high (regio)selectivity, excellent functional group tolerance, and high yields.