Complexing of terpenes with transition metals. Part IV. A comparison of the reactions of (+)-3,7-dimethylocta-1,6-diene with palladium(II) and with mercury(II)

Abstract

With palladium(II) chloride (+)-3,7-dimethylocta-1,6-diene may, depending on the conditions, undergo Wacker oxidation to 3,7-dimethyloct-6-en-2-one, or yield a Pd π-allyl derivative of 2,6-dimethyloct-2-ene and α-terpineol (p-menth-1-en-8-ol) by a process of intermolecular hydrogen transfer. Conversely, mercury(II) acetate in aqueous tetrahydrofuran initiates Markownikoff cyclisation to give, after reduction, isomeric 2-(2,3-dimethylcyclopentyl)propan-2-ols, the stereochemistry of which is deduced. Mercury(II) acetate in methanol or propan-2-ol leads mainly to acyclic products. Strongly acidic conditions cyclise 3,7-dimethylocta-1,6-diene to a trimethylcycloheptyl cation which may be trapped under the conditions of the Koch reaction.