Science of Synthesis

Chartoire, A.; Nolan, S. P., Science of Synthesis: Cross Coupling and Heck-Type Reactions, (2013) 1, 521.

Some palladium- and fluoride-free procedures are available in the literature for the cross coupling of alkynylsilanes. These procedures require a polar solvent such as 1,3-dimethylimidazolidin-2-one or dimethylformamide to allow the transmetalation from silicon to copper and subsequently promote the reaction. For example, the 1,3-diynes ‌32‌ are prepared using a catalytic amount of copper(I) chloride in dimethylformamide at 80 °C starting from the alkynylsilanes ‌30‌ and an alkynyl chloride ‌31‌ (‌Scheme 9‌).[‌36‌] The diynes ‌32‌ are generally obtained in moderate yields due to a side reaction involving the homocoupling of the silane derivative. Another example is the preparation of the 1,3-enynes ‌35‌ starting from alkynylsilanes ‌33‌ and vinyl iodides ‌34‌. The process makes use of an excess of copper(I) chloride in 1,3-dimethylimidazolidin-2-one and tributylamine at 120 °C. Under these conditions, the homocoupling side reaction is not observed, but an excess of copper salt as well as high temperature are necessary to promote the reaction.[‌37‌] Finally, alkynylsilanes ‌36‌ can be coupled with some acyl chlorides ‌37‌ to yield efficiently the alkynyl ketones ‌38‌.[‌38‌] The reaction requires either 20 mol% or 1 equivalent of copper(I) chloride in 1,3-dimethylimidazolidin-2-one at 80 °C. The procedure is only effective for acyl chlorides, and the use of acyl bromides affords low conversions.

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M8	M8	Meeee (%)	Mee
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Meeeee ‌88‌; Meeeeee Meeeeeeee:[‌88‌]

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Meeeee ‌88‌; Meeeeee Meeeeeeee:[‌88‌]

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Meeeee ‌88‌; Meeeeee Meeeeeeee:[‌88‌]

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References