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Author Topic: cyclization of N-substitued benzene-1,2-diamine with imidates  (Read 2303 times)

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kriggy

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cyclization of N-substitued benzene-1,2-diamine with imidates
« on: August 07, 2018, 09:09:26 AM »

hey, Im doing this reaction in refluxing acetic acid and it works perfectly, high purity, high yield. However, since Im trying to make axially chiral compound, I was thinking using a chiral acid catalyst for the cyclization. Did that in refluxing toluene with 10-camphorsulfonic acid but the reaction is mess, it shows maybe 5 different products. Any idea what might be the cause? Is sulfonic acid too strong acid so it protonates my amine which leads to some side reaction? I did the reaction with BF3.OEt which seems to be stronger acid but that works well.
My boss suggested using weaker acid which im gonna do this week but looking for more opinions of experienced chemists.


phth

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Re: cyclization of N-substitued benzene-1,2-diamine with imidates
« Reply #1 on: August 08, 2018, 07:54:28 PM »

Yeah, it should work, maybe the ions are not pairing at refluxing temperatures, or the rates of side reactions are too fast with CSA. You could try a chiral phosphoric acid, or lower temperature with the stronger acid... maybe 60ยบ or room termperature
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kriggy

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Re: cyclization of N-substitued benzene-1,2-diamine with imidates
« Reply #2 on: August 08, 2018, 08:38:35 PM »

Yeah thanks, I did try it in refluxing toluene again with mandelic and tartaric acid and it was the same, however, it seems to be working somehow in methanol at RT (the conversion seems to be bad but at least im getting 80%ee)
I was looking into some chiral phosphoric acids but they seem to be way too expensive.
« Last Edit: August 08, 2018, 11:01:39 PM by kriggy »
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