Abstract
The cyclic olefin, 3-carene, undergoes an isomerization of the carbon-carbon double bond to produce 2-carene, a precursor in the synthesis of (−)-menthol. This isomerization is observed over silica supported nickel, but the selectivity is reduced by side reactions producing trimethylheptenes by hydrogenative ring opening of the cyclopropyl ring. Selectivity for CC bond isomerization is dramatically increased by surface modification of the nickel metal catalyst by reaction with tetra-
n-butyl tin. The most selective of these silica supported nickel/tin catalysts produces 2-carene with 91% selectivity at 48% conversion.