An overview is given of the use of the Heck reaction for the production of
fine chemicals. Five commercial products have been identified that are prod
uced on a scale in excess of 1 ton/year. The herbicide Prosulfuron(TM) is p
roduced via a Matsuda reaction of 2-sulfonatobenzenediazonium on 3,3,3-trif
luoropropene. The sunscreen agent 2-ethylhexyl p-methoxy-cinnamate has been
produced on pilot scale using Pd/C as catalyst. Naproxen(TM) is produced v
ia the Heck reaction of 2-bromo-6-methoxy-naphthalene on ethylene, followed
by carbonylation of the product. Monomers for coatings are produced via a
Heck reaction on 2-bromo-benzocyclobutene. A key step in the production of
the antiasthma agent Singulair(TM) is the use of the Heck reaction of methy
l 2-iodo-benzoate on allylic alcohol (18) to give ketone (20). The high cos
t of palladium has spurred much research aimed at the development of more a
ctive palladium catalysts. Ligandless catalysts are very attractive for pro
duction, but work only on reactive substrates. Palladacycles are much more
stable than Pd-phosphine complexes and can be used at higher temperatures.
The same effect has been reached with pincer ligands. Bulky ligands lead to
coordinatively unsaturated Pd-complexes, which are highly active for the H
eck reaction. Recycle of palladium catalysts is also very important to redu
ce cost. Immobilization of catalysts by attaching ligands to solid support
is not very useful, because of leaching and reduced activity. In ligandless
Heck reactions the catalyst can be precipitated on carriers such as silica
, dicalite, or celite. This material can be restored to its original activi
ty by treatment with I-2 or Br-2.