Lithium acetylide-ethylene diamine complex

An alternate ethynylating reagent is the lithium acetylide-ethylene-diamine complex which is available commercially. This reagent in dimethyl sulfoxide solution has been used to ethynylate 11 j -hydroxyestrone and its 3-methyl ether. 

An ethynylation reagent obtained by decomposition of lithium aluminum hydride in ethers saturated with acetylene gives a satisfactory yield of (64), Best results are obtained with the lithium acetylide-ethylene diamine complex in dioxane-ethylenediamine-dimethylacetamide. Ethynylation of (63) with lithium acetylide in pure ethylenediamine gives (64) in 95% yield. 

Sodium acetylides are the most common reagents, but lithium, magnesium and other metallic acetylides have also been used. A particularly convenient reagent is lithium acetylide-ethylene diamine complex. Alternatively, the substrate may be treated with the alkyne itself in the presence of a base, so that the acetylide is generated in situ. 1,4-Diols can be prepared by treatment of aldehyde with dimetalloacetylenes. 

Longer-chain alkyl halides may not be commercially available, but they are readily made in one step from the corresponding alcohols (Larock, 1999), as are tosylates and mesylates. Similarly, longer-chain terminal alkynes are not commercially available, but can be readily made by reaction of alkyl halides with lithium acetylide-ethylene diamine complex in dry... 

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