Borane anions nucleophilic substitution

In the past, carbanions of propynoate esters have been difficult to obtain cleanly owing to nucleophilic attack of the base used (e.g. Bu"Li) on the ester function. It has now been found that such anions are readily available using the ubiquitous base lithium di-isopropylamide. Furthermore, subsequent reactions of such anions with a trialkyborane followed by decomposition of the borane complex with iodine afford high yields (70—80%) of substituted alk-2-ynoates. ... 

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