Dihydromyrcenol carbonylation catalyzed by palladium–tin precursors: selectivity of the reaction drawn by the experimental conditions and the co-reactants

The methoxycarbonylation of dihydromyrcenol 1 has been carried out in the presence of the catalytic system [PdCl2(PPh3)2]–SnCl2·2H2O–2PPh3. This study shows that it is possible to reduce the amounts of isomerization of the terminal double bond and the dehydration side-reaction of the tertiary alcoholic function. According to the experimental conditions (PCO=40 or 100 bar, concentration of methanol, experiment duration, temperature) it is possible to orient the reaction towards the three ‘linear’ esters 4, 5, 6, and lactone 8. This latter product has been exclusively obtained when the acidity of the medium is controlled. Nevertheless it is more difficult to obtain one ester from each others.