A new phosphine-imidazolium salt, L.HBr (1 . HBR = (1-ethylenediphenylphosp
hino-3-(mesityl))imidazol-2-ylidene), has been prepared, A combination of 0
.5 mol % of Pd(dba)(2) and 0.5 mol % of L . HBr in the presence of 2 equiv
of Cs2CO3 as base has proven to be highly efficient in the Heck coupling re
actions of aryl bromides (from electron deficient to electron-rich aryl bro
mides) with n-butyl acrylate.