Rates and Regioselectivities of the Palladium-Catalyzed Ethynylation of Substituted Bromo- and Dibromobenzenes

Article abstract of DOI:10.1021/jo00279a040

The Pd(0)/Cu2Br2-catalyzed ethynylation of 1,2-dibromo-4-nitro- and 1,2-dibromo-3-nitrobenzenes provide rapidly the product in which the bromine para or ortho to the nitro group is displaced, whereas the corresponding dibromoacetamidobenzenes provide the product of meta displacement slowly.Investigation of the rates of a series of para-substituted bromobenzenes indicates that the reaction is zero-order with respect to the heptyne and bromobenzene concentration, with a Hammett ρ value of 2.8.