Copper-Promoted Cycloaddition of Diazocarbonyl Compounds and AcetylidesWe acknowledge financial support from the NIGMS (GM074822) and UT Southwestern (J.M.R is a Southwestern Medical Foundation Scholar in Biomedical Research)

1,3-Dipolar cycloaddition reactions provide convenient access to carbocyclic and heterocyclic five-membered ring systems. In some cases, 1,3-dipoles react with dipolarophiles without activation of either component. For example, the ozonolysis of olefins and the addition of nitrile oxides to alkynes often proceed without added promoters. With many substrate combinations, however, no cycloadduct is formed when the dipole and dipolarophile are simply mixed. To accelerate these types of reactions, two complementary strategies focus on modulating the reactivity of the dipolarophile (Scheme 1). In the first, Lewis acids are included to