Divergent Construction of Macrocyclic Alkynes via Catalytic Metal Carbene C(sp²)–H Insertion and the Buchner Reaction

A catalytic macrocyclization reaction of alkyne embodied diazoacetates through metal carbene intermediates is described. This method provides a variety of functionalized 13- to 20-membered cycloalkynes in synthetically useful yields under mild reaction conditions. In the presence of a copper-catalyst, the C­(sp2)–H insertion takes place dominantly with the tethered nucleophilic aniline species. Alternatively, the Buchner reaction with tethered aryl group occurs selectively when the reaction is catalyzed by a dirhodium complex. Notably, this is the only example of using metal carbene C–H functionalization and Buchner reactions for the direct and selective construction of cycloalkyne frameworks.