Copper‐Catalyzed Olefinic C(sp2)−H Activation/Carbene Insertion/Ester Hydrolysis/Cyclization with Aryl Diazo Esters for the Synthesis of Multisubstituted Furanones

A copper‐catalyzed olefinic C(sp2)−H activation/carbene insertion/ester hydrolysis/cyclization sequence has been developed for the synthesis of substituted 2(5H)‐furanones employing readily available enaminones and aryl diazo esters as substrates. This method features operationally simple and good functional group tolerance. The transformation could be scaled up to gram quantities and the obtained 2(5H)‐furanone derivatives could be easily converted to a wide range of useful synthetic building blocks, indicative of the applicability of the synthetic strategy. Isotope labeling experiments demonstrated the ester group of diazo esters was hydrolyzed during the reaction.