PLATINUM(II) MEDIATED OXIDATION OF REMOTE C-H BONDS IN FUNCTIONALIZED ORGANIC-MOLECULES

The oxidation of remote C-H bonds of aliphatic alcohols, carboxylic acids, sulfonic acids and phosphonic acids by the Pt-II ion in water was examined. The reactions were very specific with respect to the degree of oxidation: only hydroxylation (or its equivalent) was observed and further oxidation to the corresponding aldehyde or carboxylic acid functionality did not occur. The order of reactivity was alpha-C-H << beta-C-H < gamma-C-H < delta-C-H for alcohols and alpha-C-H << beta-C-H < gamma-C-H greater than or equal to delta-C-H for the acids. The reactions are thought to proceed by the initial coordination of the functional group followed by the formation of an intermediate platinacycle upon C-H activation. The observed regioselectivity arises from the tendency to form the metallacycle with the least ring strain. It was possible to make the oxidations catalytic in Pt-II by the addition of a reoxidant, such as K2PtCl6.