Alkyl sulfonates with acetylides

As noted above, alkyne anions are very useful in Sn2 reactions with alkyl halides, and in acyl addition reactions to a carbonyl.46 Alkyl halides and sulfonate esters (tosylates and mesylates primarily) serve as electrophilic substrates for acetylides. A simple example is taken from Kaiser s synthesis of niphatoxin B, in which propargyl alcohol (36) is treated with butyllithium and then the OTHP derivative of 8-bromo-1-octanol to give a 47% yield of 37.48... 

The sodium acetylide solution thus prepared may be used for a variety of organic syntheses by the addition of alkyl halides, sulfates, sulfonates, ketones, aldehydes, and esters. Where a fine suspension of the dry acetylide is desired in an inert solvent such as ether or a hydrocarbon, the solvent is added to the ammonia solution and the mixture is stirred whde the ammonia is evaporated. Extra solvent must be used to replace that entrained by the ammonia, the last traces of which are removed by a period of refluxing. Such a suspension gives better yields of, for example, propiolic acid (by the reaction with carbon dioxide) than sodium acetylide prepared in any other way. 

Even if not impaired by side reactions, the condensation of lithium, sodium, or potassium acetylides with alkyl halides is only moderately fast in ethereal media unless alkyl iodides or sulfonates are applied. Good results can be obtained in liquid ammonia. To speed up the reaction with primary alkyl bromides in THF, they may be performed in the presence of 10% of sodium iodide, in other words, under halogen/halogen exchange conditions. Polar solvents such as dimethylformamide (DMF) are mandatory with alkyl bromides and, a fortiori, chlorides. ... 

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