ANALYSIS
Using the carbene in the desired Sonogashira reaction was quick to fail experimentally. Once my goal had shifted, the reaction parameters were evaluated in an effort to maximize the yield of the new reaction. The solvent was the first variable that was evaluated. The solvents barely had any effect on the reaction, but Dioxane was the easiest to use. In the case of DMF, DMSO, and Acetonitrile, complex mixtures were formed and the desired product could not be isolated. For that reason no yield was recorded for any of those solvents. The percent of the carbene ligand was then evaluated. It had a clear effect on the yield. 20% carbene was found to be the highest producing quantity at 27.9% yield.
The base was then evaluated. In the end Nat-BuO was the best for the reaction. Though Nat-BuO was the best, there was little difference caused by the bases except in the case of Kt-BuO that produced no yield. The time needed to complete the reaction was also evaluated. Throughout several aliquots it was determined that the reaction needed only 1 hour to run to completion. I also determined that the reaction will run on just Pd(OAc)2 but is most efficient when run with both catalyst and co-catalyst. It is unfortunate that in the end the reaction was unsuccessful, but I'm glad I had the opportunity to further my learning in such a meaningful way.
REFLECTIONS
Failure is but a stepping stone.
Reaction conditions were evaluated in the Sonogashira Reaction and I found that the caffeine derived carbene does not function as a ligand for this reaction. I found that it promoted the self coupling of phenyl acetylene. I investigated the best conditions in order to optimize this secondary reaction. I found that Dioxane, Nat-BuO, and 20% ligand in the presence of both catalyst and co-catalyst were the best conditions for this reaction. None of the condition produced results according to our standards and future work is not worth my time. I have observed that the caffeine derived carbene does work as a ligand in bioinorganic processes, just not specifically for the Sonogashira reaction. The investigation will be left behind due to the little progress we’ve made toward improving the reaction.