Metathesis of methyl-1-alkenes over a CsNO 3-Re 2O 7-Al 2O 3 catalyst

Abstract

Homometathesis and cometathesis of seven kinds of methyl-1-alkenes containing from six to eight carbon atoms were carried out over a CsNO 3-Re 2O 7-Al 2O 3 catalyst in a continuous-flow system at atmospheric pressure in the liquid phase. The effects of structure of the starting alkenes on reaction behaviors, reactivities and stereoselectivities of reaction products were investigated. Most of the reactants were metathesized with high selectivity, but the main reaction in the metathesis of 2-methyl-1-hexene was double bond shift isomerization to 2-methyl-2-hexene. The reactivity of a series of methyl-1-alkenes was affected greatly by the position and the number of methyl groups. The nearer the methyl substituent to the double bond, the greater the decrease in reactivity. Likewise, the greater the number of methyl groups, the greater the decrease in reactivity. The trans/ cis ( t/ c) ratio of reaction products changed greatly according to the degree of conversion. The (t/c) 0 ratio of most reaction products was 2.4 – 2.6, showing that the position and the number of methyl groups did not greatly affect the stereoselectivity. However, 4,7-dimethyl-5-decene produced by the metathesis of 3-methyl-1-hexene had a high cis content and the ( t/ c) 0 was 0.85.