1-IODO-2-(TRIMETHYLSILYL)ACETYLENE 97

Physical properties

bp 96 °C, 55 °C/20 mmHg; n20 D 1.5110; d 1.46 g cm?3, fp 48°C.

The Uses of 1-IODO-2-(TRIMETHYLSILYL)ACETYLENE 97

(Iodoethynyl)trimethylsilane is widely used as alkyne coupling reagent predominantly used in conjunction with organocopper species or palladium catalysis.(Iodoethynyl)trimethylsilane has been largely confined to aryl- and vinylcopper coupling, where it serves well since the reverse procedure, i.e. coupling with alkynylcopper reagents, is not straightforward due to the lack of reactivity of alkynyl moieties bound to copper.

The Uses of 1-IODO-2-(TRIMETHYLSILYL)ACETYLENE 97

1-Iodo-2-(trimethylsilyl)acetylene may be used to investigate the reactivity of diamagnetic cobalt(I) complex, Tol-BDI((2-pp)2)Co [Tol-BDI((2-pp)2)H = 2-(4-tolyl)-1,3-bis(2-isopropylpyridyl)propenediimine]. It may be used for the synthesis of 1-(4-trimethylsilanylbuta-1,3-diynyl)pyrene, via Pd-coupling with 1-iodo-2-trimethylsilylacetylene.

Preparation

All involve iodination of trimethylsilylacetylenes. Direct iodination of metalated (lithium or magnesium) trimethylsilylacetylene has been largely supplanted due to the modest yields obtained. Utilizing trimethylsilylacetylene and bis(trimethylsilyl) peroxide in the presence of copper(I) iodide gives good yields. Substituting zinc iodide requires using the lithium acetylide. Copper(I) iodide (0.05 equiv.) in the presence of iodine, sodium carbonate, and a phase-transfer catalyst gives good yields without having to use n-butyllithium or a Grignard reagent to first deprotonate the trimethylsilylacetylene. The most popular procedure uses bis(trimethylsilyl)acetylene, treating it with iodine monochloride in dichloromethane at 25°Cto obtain excellent yields of (iodoethynyl)trimethylsilane.