[3 + 2] Cycloaddition of α‑Aryl-α-diazoacetates with Terminal Alkynes via the Cooperative Catalysis of Palladium and Acid

Palladium and acid cooperative catalysis is presented as a strategy for the [3 + 2] cycloaddition of acceptor/donor-type diazo compounds with terminal alkynes. The [3 + 2] cycloaddition of α-aryl-α-diazoacetates with terminal alkynes proceeded smoothly to produce 2,3,5-trisubstituted furans with high yields. This synthesis method provided a direct and efficient pathway to prepare furan ring-containing organosilane and organoboron reagents. Synthetically valuable functional groups such as chloro and bromo atoms, methoxycarbonyl, and carbonyl remained intact during the [3 + 2] cycloaddition reaction.