The tetraphosphine cis,cis,cis-1,2,3,4- tetrakis(diphenlylphosphinomethyl)c
yclopentane associated to [PdCl(C3H5)](2) catalyses the Heck reaction of bu
tyl acrylate with a wide range of sterically demanding aryl bromides, furni
shing the addition product in high yields. Turnover numbers as high as 30-8
9000 have been obtained using ortho-substituted aryl bromides and 43-2600 w
ith di-ortho-substituted aryl bromides in the presence of this catalyst.