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Author Topic: knoevenagel condensation  (Read 114 times)

zajcek01

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knoevenagel condensation
« on: October 01, 2009, 12:34:22 PM »
Does anyone know, if ammonium acetate could be substituted with triethylamine in condensation of indole-3-carboxaldehyde with nitroethane.
If this would be possible, it would be easier to purify the end product with one step less. It would be reacted as normal, evaporated excess reagents and
recrystalized from alcohol.
(I have searched the whole web, and only Shulgins procedure with ammonium acetate was found)
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Douchermann

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Re: knoevenagel condensation
« Reply #1 on: October 01, 2009, 04:22:29 PM »
Try it on small scale, then report your results back.  Experiment, my friend, experiment. haha

poisoninthestain

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Re: knoevenagel condensation
« Reply #2 on: October 01, 2009, 05:55:53 PM »
I've seen cyclic amines used before successfully so I'd imagine an alpalitic one would work as well.

The ammonium acetate works as an alkaline base for the substrate to react with, because it's conjugated base in stronger than it's conjugated acid this works fantastic...so whether you're using ammonium acetate or an organic base such as an amine, it all works the same...I've only ever used ammonium acetate which works wonderfully.

I would bet my money on it that triethylamine would work just as well as ammonium acetate. Like Douchermann said, experiment is king.

zzhuchila_clocker

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Re: knoevenagel condensation
« Reply #3 on: October 01, 2009, 07:35:24 PM »
afaik, ammonium acetate in nitroethane condensations is having some special mechanism of action, i dont remember exactly which, probably it is both an acid and base. but it is not simply base, otherwise the best catalyst should have been alkaline.  triethylamine should work, but better to search for examples if it is used in condenstin BA and NE(i hope these are known abbreviations). If not, then it may be not a proper catalyst
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poisoninthestain

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Re: knoevenagel condensation
« Reply #4 on: October 01, 2009, 08:03:35 PM »
Quote from: zz-zhuchila on October 01, 2009, 07:35:24 PM
afaik, ammonium acetate in nitroethane condensations is having some special mechanism of action, i dont remember exactly which, probably it is both an acid and base.

You're right it works as both an acid and a base. I should've been more descriptive. I believe it acts as more of a base than an acid though.
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