Total Synthesis of Methyl 1,5,8-Trimethoxy-1H-isochromene-3-carboxylate and Its Derivatives via Palladium-Catalyzed Annulation of 2-Alkynylbenzaldehydes
A 7-step totalsynthesis of methyl 1,5,8-trimethoxy-1H-isochromene-3-carboxylate and a 5-step synthesis of its C-3 derivatives are reported. Sonogashira coupling of 2-halobenzaldehydes with terminal acetylenes was employed to access 2-alkynylbenzaldehydes, which underwent a Pd-catalyzed annulation to afford the corresponding isochromene-containing products.