Salt promoters ruthenium catalysis

The observed ratio of [HRu3(CO)n] to [Ru(CO)3I3] in solutions after catalysis is sometimes found to vary from the 2 1 ratio shown by (59). This may be expected if acids or bases (e.g., a basic solvent) are involved in oxidation or reduction processes, which can interconvert the two such equilibria can change with pressure (193). Nevertheless, these two species are normally observed to be stable under catalytic conditions, and a combination of the two is found to provide the optimum catalytic rates (e.g., see Fig. 21). Catalyst solutions derived from nonhalide salt promoters are presumed to contain [HRu3(CO)n] and an oxidized ruthenium species analogous to [Ru(CO)3I3]-, although no detailed studies of such systems have been reported. 

Ruthenium/Br0nsted Acid System The tandem isomerization/Friedel-Crafts reaction of aUylamides reported by Sorimachi and Terada was another early example of a cascade catalysis procedure using Brpnsted acid and metal salts as catalysts (Scheme 2.93) [127]. With the promotion of the ruthenium catalyst 342, the aUylamides isomerized to enamide X32, which was then tautomerized by a Brpnsted acid (343 or 344) to form imine X33 then the electron-enriched aromatic substrates 341 attacked the Brpnsted acid-activated imine intermediates to afford Friedel-Crafts products 345 in up to 91% yield. 

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