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

Abstract

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[subscript n] trans internal olefins into C[subscript 2n–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)(C[subscript 3]H[subscript 6])(pyr)(OHIPT) (Ar = 2,6-diisopropylphenyl; pyr = pyrrolide; OHIPT = O-2,6-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])[subscript 2]C[subscript 6]H[subscript 3]) and various [CpRu(P–N)(MeCN)]X (X[superscript –] = [B(3,5-(CF[subscript 3])[subscript 2]C[subscript 6]H[subscript 3])[subscript 4][superscript –]], PF[subscript 6][superscript –], B(C[subscript 6]F[subscript 5])[subscript 4][superscript –]) isomerization catalysts.