Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: jeffwm on August 19, 2015, 12:47:33 PM
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Hello all,
I have been trying do a reaction that published very high yields and great reproducibility for quite some time now. It involves reacting ethyl indole-2-carboxylate with 3-formylpyridine. The conditions are supposed to be in ethanol @RT for 8hrs with TMG (1,1,3,3-tetramethylguanidine). It's supposed to be a very simple reaction that couples the two SM at the 3 position of the indole, making an alcohol where the aldehyde once was.
I have taken NMR of both the indole and aldehyde SM and they are textbook clean. My ethanol is stilled freshly. But for some reason, I only get starting materials on TLC. I have done the following to troubleshoot:
let react for up to 36 hrs @RT, gentle heatings of 50C for up to 36hrs, refluxed for up to 36 hrs, add excess TMG, make the indole excess, make the aldehyde excess, varied the solvent with 4 others
yet I still only get the starting material for this simple reaction.
I was wondering if anyone had any suggestions/has used TMG before themselves and also had an issue with it performing properly. My TMG is less than a year old and is stored under nitrogen in our lab's fridge wrapped with parafilm.
Thanks in advance for any help/suggestions, it's greatly appreciated
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I'm not sure what the precedent is that you're citing, the only hit in reaxys for these two reagents is given below. Is it a very recent paper? Otherwise I'm not sure whether the precedent really exists.
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I think TMG forms a forms a complex with CO2, so it's worth distilling before use (from CaH2 say). Is yours yellow/orange? If so, that might be worth a go. I've used it for HWE reactions before, and had trouble getting those to go before I did that...