Ethenolysis is a specific cross metathesis reaction between an internal olefin and ethylene to produce terminal olefins. Scheme 1 demonstrates the ethenolysis reaction:
Examples of ethenolysis include the conversion of a mixture of ethylene and 2-butene into propene (as in the Phillips triolefin process and the Meta-4 process developed by the Institut Français du Pétrole), and the conversion of a mixture of ethylene and 2,4,4-trimethyl-2-pentene into neohexene. These processes typically use heterogeneous, ill-defined olefin metathesis catalysts based on tungsten and rhenium oxides and which are not compatible with air, water, oxygenates, and many functional groups. The ethenolysis reaction has also been implemented in the conversion of seed oil-derived substrates such as fatty acid methyl esters (FAME) into terminally unsaturated carboxylic acids (e.g., 9-decenoic acid) and terminal olefins (e.g., 1-decene). The ethenolysis of FAME was originally performed with a heterogeneous, ill-defined rhenium catalyst to give turnover numbers (TON) of about 100. More recently, the ruthenium alkylidene catalyst Cl2(PCy3)2Ru═CH—CH═CPh2 was used for the ethenolysis of methyl oleate (MO). Several groups have used the so-called “first generation” Grubbs catalyst Cl2(PCy3)2Ru═CHPh (“C823”) or the first generation Grubbs-Hoveyda catalyst (“C601”) to promote the ethenolysis of vegetable oil-derived materials. Additionally, first generation Grubbs-like complexes that contain bicyclic phosphines were used in the ethenolysis of methyl oleate, although the highest ethenolysis turnover number reported to date for this reaction is 15,400. The cross metathesis of 1-butene and 11-eicosenyl acetate is reported, but this reaction is described to occur at 0° C. and high catalyst loading (e.g., 5 mol % catalyst loading; see example 9 in U.S. Pat. No. 6,900,347). Accordingly, there is a need in the art for a more efficient method to produce terminal olefins from internal olefins.
It is therefore desirable to provide a convenient and effective route for the production of terminal olefins. Compared with known metathesis methods, an ideal process would: substantially reduce the amount of catalyst that is needed for the cross-metathesis reaction; allow the use of a mixture of internal olefins from a variety of sources; and allow the use of a variety of alpha-olefin cross metathesis partners. Unlike the process described in U.S. Pat. No. 6,900,347, which required significant cooling of the reaction mixture, an ideal process would allow for flexibility of reaction conditions.