Ball milling, a novel and solvent-free mechanochemistry method, was implemented with the goal of creating greener carbon-carbon bond syntheses through nucleophilic substitution. To begin this process, a carbon nucleophile needed to be created. Typically, alkyne deprotonation to produce an acetylide ion requires strong and harsh bases which tend to be hazardous to humans and/or the environment. This project shows the use of safer bases, particularly hydroxides, to achieve the same deprotonation in ball milling conditions. The terminal alkyne, phenylacetylene, was deprotonated in the ball mill using variable mole ratios of safer metal hydroxides. The most efficient condition was the combination of cesium fluoride and lithium hydroxide, which undergoes an ion-pair switch to form cesium hydroxide and lithium fluoride in milling conditions. D<sub>2</sub>O studies were performed to monitor deprotonation with the best percentage being 89% deprotonation using 1.00 moles of phenylacetylene and a two to four mole ratio of CsF and LiOH. Interestingly, (Z)-(1,4)-diphenylbut-1-ene-3-yne was found to be the main product when a 2:4 mole ratio of CsF:LiOH reacted with phenylacetylene for at least 300 minutes. Once a desired percentage of deprotonation was found alkyl halides were added to the reaction to create carbon-carbon bonds. GC-MS and <sup>1</sup>HNMR revealed a small amount of desired product which shows promise with further optimization. Overall, a green solvent free process of deprotonating a terminal alkyne was found and a potential process to create carbon-carbon bonds has been determined.

Benign alkyne deprotonation in the high speed ball mill

2019 Spring National Meeting

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