Platinum Metals Rev., 1997, 41, (4), 163
Palladium/Porous Glass Catalysts for Heck Reactions
Palladium catalysts are often used for the activation of C-H bonds, and in particular, there has been much work on palladium-catalysed Heck reactions. However, commercial development has so far been hampered by the low turnover numbers and turnover frequencies obtained. Palladium catalysts are also susceptible to poisoning, and therefore, relatively large amounts (1–5 mol%) of metal are required.
In order to overcome these problems, researchers from the CSIRO Division of Molecular Sciences, Australia, have used ∼ 0.18 per cent palladium metal on porous glass tubing as a catalyst for liquid phase organic coupling reactions (J. Li, A. W.-H. Mau and C. R. Strauss, Chem. Commun ., 1997, (14), 1275–1276).
This catalyst, which could be used in continuous or batchwise reactions, is resistant to oxidative deterioration and can be reused several times; in most cases, the reactions can be performed in air.
The regioselectivity observed is mostly consistent with previously reported Heck reactions with terminal alkenes yielding about 80:20 mixtures of 1- and 2-arylated alkenes. This catalyst also gave good yields for the coupling of terminal acetylenes with aryl iodides and bromides to give internal alkynes without the need for solubilising or activating ligands.
It is suggested that this system could find uses in other palladium catalysed reactions, such as hydrogenations and dehydrogenations.