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Topic: Alkyl Gallate Synthesis (Steglich Esterification)  (Read 2785 times)

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Offline jvinlim

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Alkyl Gallate Synthesis (Steglich Esterification)
« on: February 26, 2024, 02:00:13 AM »
For my small research, the compounds that I want to synthesize are alkyl gallates (ethyl gallate, butyl gallate, and hexyl gallate). The overall reaction:

Gallic Acid + Alcohols + (THF, DCC, DMAP, 0 Celsius) ---> Alkyl Gallates + DCU

However, from reading some literature, it's mentioned that using DCC in Steglich esterification has drawbacks; it produces a by-product (DCU) and can prove difficult to remove remaining trace amounts.

My question:
    • Are there any effective methods to remove the DCC by-product and the remaining trace amounts? If there are, could you tell me in detail about the methods?
    • Is THF a suitable solvent for this reaction, or are there other solvents that might be more appropriate?
    • What do you think about the reaction temperature, should I just do it at Room Temperature or keep it at 0 celcius
    Important Note:
    I'm aware that I could use DIC or EDC to prevent this problem, but I don't have DIC or EDC, and I'm trying to avoid purchasing them because they're pretty expensive in my country.[/list]

    Offline Babcock_Hall

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    Re: Alkyl Gallate Synthesis (Steglich Esterification)
    « Reply #1 on: February 26, 2024, 10:29:08 AM »
    Is it known that the phenolic -OH groups of gallic acid do not react?  If they did, they would have to be protected, to avoid formation of dimers, trimers, etc.

    Some DCU is filtered off; it is conceivable that the rest will be removed by purification over silica.  I recommend wearing gloves and disposing of small amounts of DCC carefully.  Some people are sensitive to this compound, which you may know already.

    Offline rolnor

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    Re: Alkyl Gallate Synthesis (Steglich Esterification)
    « Reply #2 on: February 28, 2024, 04:55:34 AM »
    I think you can buy these compounds, or? Agree, you need to protect the hydroxyl groups. Then just make the acid chloride with SOCl2 and dissolve the acid chlorides in the alcohol with 1 eqv.  pyridine present.
    Protecting group could be benzyl, you hydrogenate to remove it.

    Here is ethyl gallate, you can buy this and protect with benzyl bromide/NaH/DMF. Then add the alcohol you want + NaH, this will transesterificate the ethyl ester to give you the ester you want, then hydrogenate to remove the benzyl groups

    https://en.wikipedia.org/wiki/Ethyl_gallate

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