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I tried refluxing in toluene using activated molecular sieves to absorb any water produced (didn't use Dean-Stark trap as it's a very small scale reaction).

This reaction isn't going by changing the time or temperature conditions. So, I added some (0.5 equivalent) triflic acid to increase the electrophilicity of the carbonyl. The reaction is proceeding but conversion isn't high. Is triflic acid a good choice for this reaction? Should I try using equivalent amount of triflic acid to increase the conversion?

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    $\begingroup$ Triflic acid is just going to protonate your diamine. Something like Ti(OiPr)4 might be a better option $\endgroup$ – Waylander Nov 26 '19 at 14:34
  • $\begingroup$ doi.org/10.1016/j.poly.2008.04.028. This might be helpful. The starting material is slightly different (phenyl group instead of methyl) but I hope following similar procedure might help. $\endgroup$ – Soumik Das Nov 26 '19 at 14:46
  • $\begingroup$ @SoumikDas I have read it already but as I said increasing temperature isn't working for me. here they have used reflux conditions only. $\endgroup$ – Suchi Ghosh Nov 26 '19 at 15:42
  • $\begingroup$ @SuchiGhosh This may be inappropriate to the question you asked. But I just wanted to know do you really need this particular reaction if it's not happening. Is there a possible way to bypass this step if you are doing a multi-step synthesis ? What might be occuring is that due to lot of methyl groups in the product, the conversion rate is not so high due to steric factors, so I was suggesting whether there can be any alternate way to reach the final goal. $\endgroup$ – Soumik Das Nov 26 '19 at 16:03
  • $\begingroup$ Actually I do need to synthesize the imidazolidine ring where there is a methyl substitution at the imidazolidine-pyridine junction. The steric effect is one of the reasons that this isn't going as expected. But in presence of acid it is converting to the desired product as the carbonyl will be more electrophilic. But I am not sure about the choice of acid. $\endgroup$ – Suchi Ghosh Nov 26 '19 at 16:15

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