POLYMER-SUPPORTED PD(II) WACKER-TYPE CATALYSTS .3. ISOMERIZATION OF ALKENE DOUBLE-BOND

A cyanomethylated polybenzimidazole coordinated to Pd(II) has been emp loyed as a Wacker-type alkene oxidation catalyst in aqueous ethanol. S tarting with alk-1-enes isomerisation to the more thermodynamically st able internal alkenes is very much faster than oxidation. Indeed after only a short time no alk-1-ene is detectable e.g. by nuclear magnetic resonance analysis. Almost certainly, however, traces of the alk-1-en e do exist in equilibrium. Irrespective of whether the starting alkene is oct-l-ene, t-oct-2-ene or t-oct-4-ene the same three products are obtained: octan-2-one, -3-one and -4-one. In the case of oct-l-ene and t-oct-2-ene the composition of the ketone product mixture is very sim ilar, although with t-oct-4-ene a significant increase in the proporti on of the Cone is observed. The major product in all cases however in the Zone, The latter almost certainly arises from rapid oxidation of a small stationary concentration of alk-1-ene, with shift of the alkene equilibria maintaining the latter. Direct oxidation of the higher alk enes to the higher ketones occurs more slowly, but contrary to other r eports this is significant.