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Topic: Imine formation from aldehyde and amine  (Read 19896 times)

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Offline linh_ngt

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Re: Imine formation from aldehyde and amine
« Reply #15 on: November 12, 2012, 07:50:36 AM »

I think it has my desire product already. This is just the crude product but I'll not purify this crude, just use for next reaction.
Do you think it's ok?
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Offline discodermolide

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Re: Imine formation from aldehyde and amine
« Reply #16 on: November 12, 2012, 08:07:46 AM »
I don't think there is much imine in there.
I would start again. Use the method Dan suggested for purifying the chloroform.
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Offline linh_ngt

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Re: Imine formation from aldehyde and amine
« Reply #17 on: November 12, 2012, 08:19:04 AM »

In this reaction, i use dichloromethane, not chloroform.
In NMR data, I observe some peaks of desire product: aromatic protons of phenyl group, proton of CH=N- bond, 4H of -O-CH2-CH2-O-, 2CH3 and there is no starting material left ( no more peak of CH of aldehyde group, for sure).
I'll try to make this reaction again using CHCl3 solvent dried by K2CO3; and also I'll try the next reaction without purification
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Offline discodermolide

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Re: Imine formation from aldehyde and amine
« Reply #18 on: November 12, 2012, 08:46:26 AM »
As far as I could see there were 24 aromatic protons in this spectrum, but it was difficult to see the number.
24 aromatic protons don't fit with the structure.
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Offline linh_ngt

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Re: Imine formation from aldehyde and amine
« Reply #19 on: November 12, 2012, 08:56:02 AM »
I think 24 aromatic protons would be include aromatic protons of amine left ( I used 1.5 eq amine compared with 1 eq aldehyde)
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Offline discodermolide

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Re: Imine formation from aldehyde and amine
« Reply #20 on: November 12, 2012, 09:00:20 AM »
I posted a method for you give that a try?
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Offline linh_ngt

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Re: Imine formation from aldehyde and amine
« Reply #21 on: November 12, 2012, 09:11:55 AM »
There is water formed in this reaction, you need to remove it. Add anhydrous magnesium sulphate to your DCM solution, and stir.
Imines are probably not stable to TLC, so be careful when interpreting tlc results. Same goes for CC. Use NMR to judge if the reaction is complete. Don't isolate it, remove the solvent and use it directly. I have a few methods for making various imines of amino acids with aldehydes.
Try this: (Note aden of Et3N is to generate the free amino group so it can react.
A suspension of the gylcine ester hydrochloride salt (other salts can also be used, for example tosylate salts) (1 equivalent) was stirred in methylene chloride for ten minutes and treated with 10 equivalents of anhydrous magnesium sulphate, and stirring continued for 1 hour at room temperature. A solution of the aldehyde (1 equivalent) in methylene chloride was added within 5 minutes at room temperature followed by dropwise addition of triethylamine or a similar tertiary organic base (2 equivalents). Stirring was continued for 20 hours at room temperature, and the mixture was filtered. The solvent was removed in vacuum to give an oily solid. Tert-Butyl-methyl ether was added slowly while stirring to crystallise the triethylamine hydrochloride, which was removed by filtration after stirring the mixture for 1 hour at room temperature. The solvent was then removed from the filtrate to give the desired imine as an oil, or in some cases a solid which were used without further purification.

Yields very very high >98%.
U mean this method??? WHen can I put my amine (1-phenyl ethylamine) because I dont see this information and I also dont have this kind of salts
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Offline orgopete

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Re: Imine formation from aldehyde and amine
« Reply #22 on: November 12, 2012, 09:58:47 AM »
Tell us what you are trying to do. I suspect you are trying way to hard and you can make your desired product a lot more easily, but I could be wrong because I don't know what you are trying to make.
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Offline linh_ngt

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Re: Imine formation from aldehyde and amine
« Reply #23 on: November 12, 2012, 10:01:40 AM »
Tell us what you are trying to do. I suspect you are trying way to hard and you can make your desired product a lot more easily, but I could be wrong because I don't know what you are trying to make.

I just wanna synthesize this imine from this aldehyde
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Offline discodermolide

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Re: Imine formation from aldehyde and amine
« Reply #24 on: November 12, 2012, 10:17:57 AM »
Look, instead of the glycine ester substitute your amine, and leave out the triethylamine. Everything else the same.
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Offline linh_ngt

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Re: Imine formation from aldehyde and amine
« Reply #25 on: November 12, 2012, 10:40:24 AM »
Leaving out of triethyl amine means that I did this method already, just change the amount of MgSO4 (10 eq--> 5eq) :)
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Offline orgopete

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Re: Imine formation from aldehyde and amine
« Reply #26 on: November 12, 2012, 12:45:00 PM »

I just wanna synthesize this imine from this aldehyde

Quote
… This is just the crude product but I'll not purify this crude, just use for next reaction.

Next reaction? Why not just react 4-methoxybut-3-en-2-one with your amine? Wait, we still don't know what you are trying to do in the next reaction. Even as naive as I may appear, the dioxolane looks suspiciously like a protecting group. If so, there must be a next reaction. If that were true, perhaps you could take a chance that not only could we suggest how to make the imine, but we could actually suggest how to get to the product of the next reaction.
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Offline linh_ngt

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Re: Imine formation from aldehyde and amine
« Reply #27 on: November 12, 2012, 04:09:29 PM »

I just wanna synthesize this imine from this aldehyde

Quote
… This is just the crude product but I'll not purify this crude, just use for next reaction.

Next reaction? Why not just react 4-methoxybut-3-en-2-one with your amine? Wait, we still don't know what you are trying to do in the next reaction. Even as naive as I may appear, the dioxolane looks suspiciously like a protecting group. If so, there must be a next reaction. If that were true, perhaps you could take a chance that not only could we suggest how to make the imine, but we could actually suggest how to get to the product of the next reaction.

Next reaction that I want to make is the reaction of Danishefsky's diene with imine to obtain the follwing compound ( attached file). Exactly the dioxolane is a protecting group :)Could you kindly give me some clues?
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Offline orgopete

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Re: Imine formation from aldehyde and amine
« Reply #28 on: November 13, 2012, 03:27:19 AM »
That makes it a horse of a different color. Is the imine of alpha-methylbenzylamine or benzylamine and butyraldehyde a known compound? I would check to see how they were made.

I don't have experience with imines of the type you are trying to prepare. I know that if one wishes to prepare an enamine of an aldehyde, what forms is the aminal with potassium carbonate. This is cracked to get the enamine. Although it seemed better that you had a dioxolane, but I don't necessarily think it survived the imine forming reaction. This looked different than what I thought the spectrum should look like, but I really don't know. I don't know what the starting materials looked like. It could be okay, but aldehydes are pretty easily enolized, etc. I could imagine competing reactions occurring here.

I cannot advise you on this particular reaction, but you should be able to find reaction conditions for more simple analogs to find optimal conditions. Given the difficulties you are incurring, the complexity of the reaction you wish to try, I would hone my technique by synthesizing a simpler intermediate first. We've all faced your question, "Is it me, or is it the reaction?" We can't answer that. You need to establish that yourself. Your conditions were plausible enough. Do they work with enolizable aldehydes? with beta-alkoxy aldehydes?
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