Lithium alkynylides preparation

The general scheme for preparation in the laboratory has a number of alternatives, the choice of a particular method being determined by the availability of the starting acetylene, r CsCH, the desired scale of the preparation (e.g. a few millimoles, 100 mmolar, 1 molar or more) and a number of other factors. The most versatile method, suitable for working on scales varying from a few mmoles to -0.5 mole, is the reaction of a lithium alkynylide with a carbonyl compound in THF(-hexane) ... 

Di(l-alkynyl)sulfides are formed in excellent yields, if (freshly distilled) sulfur dichloride is added to a solution or suspension of a lithium alkynylide in Et20 [106). In an analogous manner, di(l-alkynyl)sulfoxides are formed from thionyl chloride and an alkynyllithium [106], while sulfinyl chlorides R S(=0)G may be used to prepare the sulfoxides RC=CS(=0)R Preliminary experiments suggest that interaction between alkynyllithium and sulfonyl chlorides R S02C1 can give both sulfones ROCSOjR and chlofo-alkynes RCsCCl [2). 

Mahyisulfonyl chloride CH3SO2CI and tosyl chloride give low to moderate yields of ROCSO2CH3 and RC=CS02-Aryl. Part of the sulfonyl chloride reacts with the lithium alkynylide to give a chloroalkyne. A more succesful method to prepare acetylenic sulfones involves Oxidation of acetylene sulfides with peiacids. 

A solution or suspension of 0.22 mol of the lithium or sodium alkynylide in 300 ml of liquid ammonia is prepared as described on p. 20. The disulfide, thiosulfonate or thiocyanate (0.20 mol, diluted with 50 ml of Et20, is added dropwise over 10 min with efficient stirring. In many cases a rather thick suspension is formed an additional volume of-100 ml of liquid... 

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