A One-Pot Tandem Olefin Isomerization/Metathesis-Coupling (ISOMET) Reaction

A tandem catalytic reaction has been developed as part of a process to discover tungsten-based olefin metathesis catalysts that have a strong preference for terminal olefins over cis or trans internal isomers in olefin metathesis. This tandem isomerization/terminal olefin metathesis reaction (ISOMET) converts C n trans internal olefins into C2n–2 cis olefins and ethylene. This reaction is made possible with Ru-based “alkene zipper” catalysts, which selectively isomerize trans olefins to an equilibrium mixture of trans and terminal olefins, plus tungsten-based metathesis catalysts that react relatively selectively with terminal olefins to give Z homocoupled products. The most effective catalysts are W­(NAr)­(C3H6)­(pyr)­(OHIPT) (Ar = 2,6-diisopropylphenyl; pyr = pyrrolide; OHIPT = O-2,6-(2,4,6-i-Pr3C6H2)2C6H3) and various [CpRu­(P–N)­(MeCN)]­X (X– = [B­(3,5-(CF3)2C6H3)4]–, PF6 –, B­(C6F5)4 –) isomerization catalysts.