A Copper-Catalyzed [5+1] Cycloaddition of Terminal Alkynes with Diazo Esters through a Tandem 1,5-H-Shift Cyclization

A copper-catalyzed [5+1] cycloaddition reaction of terminal alkynes with diazo esters for the rapid construction of protected naphthalen-1(2H)-one derivatives in moderate to good yields has been disclosed along with good functional group compatibility and a broad substrate scope. The mechanistic investigations reveal that this tandem cyclization process proceeds through a Cu(I)-catalyzed coupling of terminal alkyne with diazoacetate, a 1,5-H shift process and a thermally induced pericyclic reaction via an allene intermediate. The synthetic utility and the further transformations of the obtained cycloadduct to naphthalenone, naphthol and dihydronaphthol have been also presented in this paper.