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20.5.1.7.12.1 Method 1: Metathesis with Tungsten-Based Catalysts

DOI: 10.1055/sos-SD-020-00774

Zhang, M.; Hanson, P. R.Science of Synthesis, (200720920.

Phenoxytungsten complexes catalyze inter- and intramolecular metathesis reactions of simple alkenoates and alkadienoates, respectively. Chloro(diethyl ether)bis(2,6-diphenylphenoxy)neopentyl(neopentylidene)tungsten(VI) was one of the first examples of tungsten complexes that are well-defined, Lewis acid free, homogeneous alkene-metathesis catalysts, and shows moderate activity for the metathesis of ethyl oleate with dec-5-ene.[‌320‌] A better result can be achieved when tetrachlorobis(2,6-dichlorophenoxy)tungsten(VI) associated with a Lewis acid (Bu4Pb or Me4Sn) is employed as catalyst (Scheme 74).[‌321‌,‌322‌] In 1995, trans-dichlorobis(2,6-dibromophenoxy)oxotungsten(VI), prepared in situ from tetrachloro(oxo)tungsten(VI) and 2 equivalents 2,6-dibromophenol, was found to catalyze ring-closing metathesis of nonconjugated dienes, e.g. 219, to form the corresponding cycloalkenes, e.g. 220 (Scheme 78).[‌323‌,‌324‌]

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