Science of Synthesis

Griesbeck, A. G.; Soldevilla, A., Science of Synthesis, (2008) 43, 385.

A convenient system has been developed for the alkyne homodimerization of aromatic alkynes, with hexacarbonylmolybdenum(0) as the catalyst and phenols as activating additives at high temperatures (see also Section ‌43.9.1.1.5‌).[‌168‌] No catalyst preactivation and no sacrificial alkyne is required; the process uses a mixture of hexacarbonylmolybdenum(0), 4-chlorophenol, and the starting alkyne in 1,2-dichloroethane at 85°C for 9–24 hours to afford the product alkyne (e.g., ‌100‌, ‌Scheme 52‌).[‌169‌] Sterically hindered molybdenum(III) amido complexes of the general type [Mo{N(t-Bu)Ar1}3] upon treatment with dichloromethane or other halogen donors have been shown to be highly effective alkyne metathesis catalysts.[‌170‌] Alkoxide complexes of the type [Et≡Mo{OC(CF3)Me}3(DME)] are more simple to generate and show high metathesis activities.[‌171‌]

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