Evidence for the existence of a cyclic ruthenium(VI) diester as an intermediate in the oxidative scission of (-)-α-pinene with RuO4

The reaction of (-)-α-pinene with RuO4 in CCl4 at room temp. affords the ketoaldehyde I as the sole product. Evidence is reported that the oxidative scission of the olefinic substrate to I proceeds through a ruthenium(VI) diester intermediate, the structure was proposed on the basis of spectral evidence and comparison with the osmium-contg. analog, synthesized by reaction of (-)-α-pinene with OsO4 in dioxane and whose structure has been detd. by single crystal x-ray diffraction anal. The diester intermediate was also shown to be an intermediate compd. in the RuO4 oxidn. of (-)-α-pinene performed in acetone-water (2:1) which gives a α-ketol as the sole oxidation product