Author Topic: Acids to amides in one step with boric acid  (Read 2041 times)

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  • Guest
Acids to amides in one step with boric acid
« on: October 30, 2004, 03:37:00 PM »
On the page 46 of

there is a claim that carboxylic acid amides can be prepared by refluxing the acid and the amine in toluene with boric acid as a catalyst. Now, this would be a very practical method that avoids going trough acid chlorides or methyl esters. The only other OTC method that I know of direct transformation of an acid to its amide is by heathing it with urea, but besides being low yielding and not that general it gives N-unsubstituted amides. This one seams to give R-CO-NR2.
The only problem is that there is no reference and I could not find any patent or literature. Anybee knows where to find a paper on this?

PS: There are also other interesting "green" methods in that link.


  • Guest
Here is the patent: US6384278
« Reply #1 on: October 30, 2004, 04:21:00 PM »
Here is the patent:

Patent US6384278

. Unfortunately it looks like the invention only works for anilines. They don't have related patents for alkylamines.


  • Guest
aromatic carboxamides
« Reply #2 on: October 31, 2004, 12:23:00 AM »
Process for the preparation of aromatic carboxamides from aromatic carboxylic acids and urea

Process for the of aromatic carboxamides from aromatic carboxylic acids and urea Process for the preparation of aromatic carboxamides of the formula (I)  (I) in which R1, R2, and R3 are identical or different and are hydrogen, fluorine, chlorine or bromine atoms, or are alkyl(C1-C4), hydroxyl or nitro groups, or R1 and R2 form an aromatic ring of 5 or 6 ring members, which ring may be substituted by fluorine, chlorine or bromine atoms or by alkyl(C1-C4), hydroxyl or nitro groups, which involves reacting aromatic carboxylic acids of the formula (II)  (II) in which R1, R2 and R3 are as defined above with urea in an inert organic solvent with the addition of a catalytic amount of phosphorous acid.

Patent EP0663390


  • Guest
Acids to amides
« Reply #3 on: October 31, 2004, 01:34:00 AM »
There are a few alternatives to synthesize amides from the corresponding carboxylic acids. Some are more convenient than others...
  • Schmidt reaction: This reaction involves the attack of hydrazoic acid on a nucleophile and is used for aldehydes, ketones and carboxylic acids. The generated isocyanate is decomposed with water.

  • Pyrolysis: Salts are prepared by reacting carboxylic acids with ammonia (or amines)

RCOOH + NH3 ---> RCOO-NH4+ ---> RCONH2

Taken from March (p 508-509): Although treatment of carboxylic acids with amines does not directly give amides, the reaction can be made to proceed in good yield at room temperature or slightly above by the use of coupling agents, the most important of which is DCC. This is very convenient and is used a great deal in peptide synthesis. They also state the method is seldomly used for preparative work since there are better alternatives.
Carboxylic acids can also be converted to the corresponding amides with phosphoric acid derivatives, trisalkylaminoboranes, sulfonic acids are with the amides of carboxylic acids:

RCOOH + (C6H5)2PONH2 ---> (C6H5)2POOH + RCONH2
RCOOH + B(NHR'2)3 ---> RCONR'2

It is also possible to use carboxylic esters.

Need a reference on one of the these?


  • Guest
Damn anilines!
« Reply #4 on: October 31, 2004, 03:12:00 AM »
How disappointing that it only works with anilines.
I don’t know how I managed to miss the patent. I searched for “boric acid” instead of “boron”, but I also searched for the company name and still missed it. :(

Saddam, thanks for listing the alternatives. I’m aware of the coupling agents and some other methods, but I was hoping this would bee a cheap and simple one-step OTC amidation method. I also know that some ammonia salts, like ammonium formate or acetate, dehydrate to their amides on heating. But, for example, if you would want to transform a more complex acid like 3-indolyl-acetic acid into its diethylamide, you would have to go trough the amonolysis of the methyl ester which is two steps (at least those of us who don’t have DCC or other coupling reagents). In such cases this method would be very cool if it would work.

Just a thought caused by the Saddam’s equation using B(NR2)3 as a reagent: I have some sulfamidic acid (H2N-SO3H). Is there any known method for this reagent to transform acids to amides?


  • Guest
R-CO-ONa + NH2HSO3 --> R-CO-NH2 + NaHSO3 ?
« Reply #5 on: October 31, 2004, 09:34:00 PM »
R-CO-ONa + NH2HSO3 --> R-CO-NH2 + NaHSO3 ? weird reaction...