Vinylarenes by Vinylation of Aromatics

Some intermediates to fine chemicals are prepared industrially by vinylation of aromatics. We have selected three well-known products as representative cases, namely an intermediate to Naproxen, a non-steroidal antirheumatic drug (Albermarle) (Equation 11) an intermediate to Prosulfuron, a potent herbicide (Ciba Geigy-Novartis) (Equation 12) and a monomer for polymerization to Cyclotene electronic resins (Dow Chemicals) (Equation 13). 

The sodium salt of 2-(3,3,3-trifluoropropenyl)benzenesulfonic acid, the intermediate to Prosulfuron, is manufactured from 2-diazobenzenesulfonate and 

3- trifluoropropene in the presence of palladium(0) and NaOAc (Equation 12). According to a patented procedure [P. Baumeister, G. Seifert and H. Steiner, EP Patent 584 043 A1 (1994), to Ciba-Geigy], aniline-2-sulfonic acid is diazotised with isopropyl nitrite in an isopropanol/water solution at 15-20°C. The diazo suspension is transferred to a pressure vessel where it is reacted with 

With aryl halides oxidative addition is often the rate-determining step this is promoted by appropriate ligands such as triarylphosphines. Finely divided palladium metal or ligand-free palladium, prepared in situ by reduction of palladium(II) species, can also be used in weak donor media. Palladium(0) with a triarylphosphine as ligand reacts with aryl halides in the order Arl ArBr ArCl. Electron-withdrawing groups on the aryl halide increase the reactivity 

Inhibition also occurs when products, substrates, or reagents acting as ligands stabilize the palladium intermediates too much, thus blocking the reaction sequence. Ligand excess may produce a similar effect. Thus many palladium-catalyzed reactions are inhibited by excess ligand whose electronic and steric properties must therefore be taken into account. 

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