Week 4: Reaction Modifications and Results

The reaction results of my fourth week have displayed results that will allow the reaction conditions to be changed in order to be the most efficient. It was observed in the previous week that there is a dominant isomer that makes the cyclization more efficient. This week, that same pyrrole condensation reaction was run on the mixed isomer product as well as the dominant pure isomer in order to gather more information regarding their reactivity. The results provided some important observations, but more trials are still needed to completely understand.

The pyrrole condensation with the mixed isomer was run  in the exact same conditions are previous runs except without the use of quinoline. Quinoline is a weaker base that was acting as a buffer for camphorsulfonic acid. I decided to run the reaction without this in order to see if it impacts the reaction time. This run resulted in a pure yield of 79% which was much higher than previous runs. Since the yield had increased without quinoline, I decided to run the same reaction except with the dominant isomer. In addition, this procedure was only run for 4 hours as opposed to 24 hours. We decided to do this because of the observation that our TLC during the reaction displayed starting material however the NMR did not. An NMR spectrum is specific to a structure where a TLC spot can be shared by multiple compounds so we decided the reaction time could be reduced. This only resulted in a 32% yield which was less than anticipated however there was no starting material in the NMR so the reaction had run to completion.  These modifications have given me a stronger understanding as well as ideas for the next week.

As the last two weeks have focused on modifying the original three-step procedure, I have used a lot of my material. This means that next week, some time will have to be dedicated to making more in order to have enough for the rest of the summer. I will also be moving my product forward in the hopes of coming closer to a known natural product. There is still work to finish however the results are on track to move me towards my goal.

Comments

  1. kmkopera says:

    This is really interesting – it sounds like there’s a lot of different variables you can tweak in these reactions to see what happens to the yield. Since running the reaction without quinoline gave you such a high yield, do you think that’s a condition you’ll stick to in the future?

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