Enantioselective Synthesis of Ten-Membered Lactones via Palladium-Catalyzed [5 + 5] Annulation.

Ten-membered lactones are the core units of many biologically active natural products but with a great synthetic challenge. Based on the principle of vinylogy, novel types of cyclic vinylogous anhydrides have been designed as five-carbon carbonyl synthons, further applied in [5 + 5] annulation with vinylethylene carbonates under chiral palladium catalysis. This strategy features excellent regioselectivity, mild conditions, and broad substrate scope, affording a range of spiro ten-membered lactones bearing oxindole and pyrrolidinone motif in excellent yield (up to 99%) with moderate to high enantioselectivity (up to 89% ee).