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Author: Subject: Use of K2CO3 instead of pyridine etc. as sacrificial base acid halide Ar-OH
tsathoggua1
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[*] posted on 20-7-2017 at 09:48
Use of K2CO3 instead of pyridine etc. as sacrificial base acid halide Ar-OH


ATM, have no pyridine or 4-DMAP (although the latter is going to be on the shopping list) so organic bases, are restricted to either isopropylamine or triethylenetetramine (ethylamine could be made via reduction of nitroethane, but I've very little nitroethane left, and not enough to spare at all, since I'm going to need monoethylamine for another synthesis before replacement nitroethane can arrive, and I need to acylate an aminophenol (as the salt, either phosphate, sulfate or possibly hydrochloride of the amine, in cold, dry acetone or in acetonitrile)

If its soluble in acetonitrile, acetone would be my first choice however, although both are available.

This is more a general question, rather than pertaining to a specific substrate, but what I want to know, is does using potassium carbonate in sufficient quantity and dilution to avoid avoid forming the freebase of the aminophenol using an acyl halide, with of course the usual dry conditions, carbonate can serve well enough for mopping up the HCl released by an acid chloride, although of course not as brilliantly as 4-DMAP would, can it not?

Also, I've read that an acid halide can be converted to the corresponding anhydride by reaction with an alkali metal carboxylic acid salt of the same acid as the acyl halide formally derives from. I've never seen reaction conditions mentioned though, such as heating, time course, solvents, only told of the possibility. Could anyone give any more detail on conversion of simple carboxylic acid halides (chlorides in this case in most cases) to the corresponding anhydrides, please?
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Loptr
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[*] posted on 20-7-2017 at 10:02


Potassium carbonate is commonly used for this purpose. I have used it to neutralize the HBr released from nucleophilic substitutions with haloalkanes.

Never prepared an anhydride. Sorry.




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