Homogeneous catalysts, Suzuki coupling

In a micro reactor, there is much more surface available than in standard reactors [18]. Thus, surface-chemistry routes may dominate bulk-chemistry routes. In this context, it was found sometimes micro-reactor routes can omit the addition of costly homogeneous catalysts, since the surface now undertakes the action of the catalyst. This was demonstrated both at the examples of the Suzuki coupling and the esterification of pyrenyl-alkyl acids. 

An der Heiden, M. and Plenio, H. (2004) Homogeneous catalysts supported on soluble polymers biphasic Suzuki— Miyaura coupling of aryl chlorides using phase-tagged palladium—phosphine catalysts. Chem. Ear. ]., 10, 1789. 

Homogeneous, aqueous tv o-phase catalysis is also of industrial interest for the production of the important intermediate phenylacetic acid (PAA), -which is used in perfume and pesticides syntheses. The previous process (benzyl chloride to benzyl cyanide -with hydrolysis of the latter) suffered from the formation of large amounts of salt (1400 kg per kg of PAA). The new carbonylation method reduces the amount of salt by 60% and makes use of the great cost difference between —CN and —CO [79-81]. Finally, the Suzuki coupling of aryl halides and arylboronic acids, substituting Pd/TPPMS with Pd/TPPTS catalysts, should be also mentioned. 

The suitability of the homogeneous aqueous catalysts and thus the scope of application in general will be extended in commercial or pilot-plant operation to other central atoms and reactions such as Heck reactions and other carbonylations (with Pd), hydrogenations (Pd, Pt, Rh, Ir), formation of water-soluble polymers (Pd), vinylations, metathesis conversions (Ru), Suzuki couplings, etc. (cf. Section 6.6). 

A. Datta, K. Ebert, H. Plenio, Nanofiltration for homogeneous catalysis separation Soluble polymer-supported palladium catalysts for Heck, Sonogashira, and Suzuki coupling of aryl halides, OrganometaUics 22 (2003) 4685-4691. 

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