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All 12 posts Subject: A 'regenerable' Friedel-Crafts acylation catalyst Please login to post Down

bottleneck
(Hive Bee)
02-01-03 19:52
No 403374
      A 'regenerable' Friedel-Crafts acylation catalyst

While searching for possible protective functions for tryptophan for use in intramolecular acylation as a possible precursor to LSD, I came across the reaction at http://www.ul.ie/~ces/ts.html under the title "Clean Chemistry Alternative to Friedel-Crafts Acylation."

The carboxylic reagent is the carboxylic acid itself (i.e., no previous derivatization required), by means of mixed anhydride formation with trifluoroacetic anhydride.

Only catalytic amounts of polyphosphoric acid are used, so although the phosphoric acid can't be regenerated, not much is lost in the process.

The "activating agent" for the phosphoric acid+mixed anhydride is also trifluoroacetic anhydride. It is used in amounts stoichiometric to the product, but after combination with the phosphoric acid and acylation of the intended aromatic substrace, trifluoroacetic acid results almost quantitatively (excepting the trace amounts bonded with the phosphoric acid).

The trifluoroacetic acid is subsequently isolated and dehydrated back to trifluoroacetic anhydride.

Presumably quite a few catalysts for the dehydration of TFA to TFAA must exist? In any event, it wouldn't hurt to have a peek at those references I guess...

Organikum
(Hive Addict)
02-02-03 05:17
No 403504
User Picture       trifluoroacetic

Trifluoroacetic acid - i am after this for some time as it is not realy OTC and also not so easy to make if you don´t sit on a big stash of teflon and love to do pyrolysis at >550°C.....
And you want to convert this to the anhydride?

Also my usual chem supplier (not supply house, more private) was not very pleased also he promised to do his best. If I had asked him for the anhydride....

Polverone wanted to bring something up with high voltage discharge, but I am not sure if he did already.

Somebody with 5 liters TFAA to much around here? Acid is ok, would take the anhydride too....

buhuu <whine> buhuu....
ORG

nothing special

bottleneck
(Hive Bee)
02-02-03 11:56
No 403570
      >Trifluoroacetic acid - i am after this for

>Trifluoroacetic acid - i am after this for some time as it is not realy OTC

I guess that would be true most places in the world. I am not really suggesting this as an OTC prep, but if someone had producion of industrial quantities in mind, maybe it deserves a second look.

> And you want to convert this to the anhydride?

Indeed. Would that be difficult? I thought there were many reagents to do this, but if nothing else works, surely dropping thionyl chloride in TFA will form TFAA?

There are a couple of methods of producing TFAA from TFA described in US6248923 (Process for the production of fluorocarboxylic acid anhydrides), like reacting with halo, di-halo or tri-haloacetic acid.

Organikum
(Hive Addict)
02-03-03 02:49
No 403819
User Picture       you are right bottleneck

The ketenelamp works here also for TFAA from TFA. My mistake I overlooked this in my emphasis concerning the bad availabilty of TFA.

Thanks for the patent so.
ORG

nothing special

Rhodium
(Chief Bee)
07-30-03 02:40
No 450648
User Picture       Regenerable Friedel-Crafts acylation catalyst
(Rated as: excellent)

Full article, retrieved by Kinetic:

Toward a Clean Alternative to Friedel-Crafts Acylation: In Situ Formation, Observation, and Reaction of an Acyl Bis(trifluoroacetyl)phosphate and Related Structures
J. Org. Chem. 63, 8946-8951 (1988) (https://www.rhodium.ws/pdf/f-c.acylation.clean.alternative.pdf)

It goes on to say that you can dehydrate TFA to TFAA using P₂O₅ on a laboratory scale, with no further details given. Anyone got a lab procedure? Or is it just to mix (carefully add oxide to acid) and distill?

I wonder if you could use this method with alanine as the acid (which would form N-TFA-alanine in situ)?
If so, then after a workup including treating the formed N-TFA-cathinone with a mild base, you would end up with a (substituted) cathinone in one pot! Starting with N-methyl-alanine would of course give methcathinones similarly...

lugh
(Moderator)
08-05-03 21:25
No 451889
      Lab Procedure

The laboratory distillation procedure was published by JM Tedder in Chemical Reviews 55, 787-827 1955 smile

Chemistry is our Covalent Bond

Aurelius
(Active Asperger Archivist)
08-05-03 22:54
No 451906
      Lugh

How do you come up with this stuff? That's either one hell of a search database you've got or an even better memory!

And if you've got the ref, why not post the procedure?

Act quickly or not at all.

lugh
(Moderator)
08-05-03 23:17
No 451911
      Time

There wasn't time to fetch the reference, perhaps some other bee can find it wink

Chemistry is our Covalent Bond

mentallyill
(Stranger)
09-06-03 00:57
No 457401
      TFA From trichloroacetic acid???

SWIM is also interested in producing TFA/TFAA. SWIM is curious about a halogen displacement reaction between trichloroacetic acid and a possible chemical such as aluminumfluoride. It seems possible that a displacement between the fluorine and the chloride should take place leaving trifluoroacetic acid and aluminum chloride. Any insight on this thought?

runs with scissors

Vitus_Verdegast
(Hive Bee)
09-06-03 02:52
No 457409
User Picture       preparation of trifluoroacetic acid
(Rated as: good read)

Couldn't find any refs on a possible halogen displacement reaction the way you suggest. Found this ref on preparation by halogen exchange :

Improved preparation of trifluoroacetic acid.
Henne, Albert L.; Trott, Paul. Ohio State Univ., Columbus, Journal of the American Chemical Society (1947), 69 1820. CODEN: JACSAT ISSN: 0002-7863. Journal language unavailable. CAN 41:30998 AN 1947:30998 CAPLUS

Abstract

cf. C.A. 39, 3253.8. Details are given of the prepn. of SbF3Cl2 from SbF3 and of its reaction with com. (CCl:CCl2)2 to give 95% crude (:CClCF3)2;oxidation with alk. KMnO4 gives 87% F3CCO2H.

If you have the necessary skills to handle anhydrous HF you might consider this. Another downside is the bad yield:

Preparation of trifluoroacetic acid by the electrochemical fluorination.
Kojima, Rimpei; Hayashi, Teiichi; Takagi, Shushi. Govt. Ind. Research Inst., Nagoya, Japan. Nagoya Kogyo Gijutsu Shikensho Hokoku (1960), 9 516-22. CODEN: NKGSAR ISSN: 0027-7614. Journal language unavailable. CAN 55:12956 AN 1961:12956 CAPLUS

Abstract

CF3CO2H (I) was prepd. by the electrolysis of glacial AcOH, Ac2O, Me2CO, or AcCl in anhyd. HF. Under the following conditions I was obtained in the highest yield by the electrolysis of 40.5 g. Ac2O and 23.5 g. Me2CO in 800 ml. anhyd. HF: current d. 2.3 and 2.8 amp./sq. dm.; total current 139 and 139 amp.-hrs.; current efficiency 10 and 9%. The yield of I was 22 and 20%, resp. In the case of glacial AcOH, by applying reversed current periodically at the interval of a few sec., the current efficiency was improved.

A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/dreamw.html)

Rhodium
(Chief Bee)
09-21-03 01:30
No 460168
User Picture       Preparation of Trifluoroacetic Anhydride
(Rated as: excellent)

The Use Of Trifluoroacetic Anhydride And Related Compounds In Organic Syntheses
J. M. Tedder
Chem. Rev. 55, 787-827 (1955) (https://www.rhodium.ws/pdf/trifluoroacetic.anhydride.pdf)

Preparation of Trifluoroacetic Anhydride (p. 821-822)

Swarts originally prepared trifluoroacetic anhydride by distilling the acid over phosphoric anhydride¹⁹³ and this remains the most convenient method of preparation for use in the laboratory. The anhydride can also be prepared by treating the acid with stabilized sulfur trioxide⁷⁷, but this method is not well suited to small-scale laboratory preparation. Because sulfur trioxide boils very close to the boiling point of trifluoroacetic anhydride [SO₃, bp 44.6°C; (CF₃CO)₂O, bp 39-40°C] it is necessary to use a slight excess of the acid. The use of sulfur trioxide comes into its own for large-scale preparations where the relative costs of phosphoric oxide and sulfur trioxide are important. Trifluoroacetic anhydride is a volatile liquid which, unlike the acid, does not fume extensively in air. Because the material is so volatile and hygroscopic, it is usually best prepared directly from the acid as and when required. Like trifluoroacetic acid the anhydride can be stored in glass vessels, but it attacks rubber, cork, and most common metals.

References
{77} Patent US2628253
{193} Swarts, F., Bull. Acad. Roy. Belg. 8, 343 (1922)

Rhodium
(Chief Bee)
10-07-03 19:16
No 463239
User Picture       Lab Prep of Trifluoroacetic Anhydride
(Rated as: excellent)

Sur l'acide trifluoroacétique
F. Swarts
Bulletin de l'Académie royale de Belgique (Classe des Sciences) 8, 343-370 (1922)

Abstract
Preparation of trifluoroacetic anhydride by dehydration of the corresponding acid using P₂O₅.
(Article freely translated from French by Rhodium)

In a distillation setup with the recieving flask submerged in a dry ice/ether mixture, 40g of P₂O₅ was placed in the distillation flask, and 16g of trifluoroacetic acid was slowly added with the aid of an addition funnel. There was no significant rise in temperature. After allowing the mixture to stand for one hour, the flask was heated to 100°C (bath temp), whereupon a relatively rapid distillation commenced, without any signs of decomposition. The distillate solidified in the reciever. It was then fractionately distilled through a short vigreaux column, care being taken to protect the liquid from atmospheric moisture, by heating gently on a water bath. The pure anhydride distilled between 39.5-40°C (corr.), again collected in a recieving flask cooled in a dry ice/ether mixture, where it solidified, mp -65°C. By vapor density measurement, it was determined that the distillate contained no trifluoroacetic acid.

Compare with the preparation of Trifluoroacetyl Triflate in Org. Syn. Coll. Vol. 7, p. 506 (http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?rxntypeid=2&prep=CV7P0506)

Also read the Trifluoroacetic Anhydride MSDS (http://www.halocarbon.com/safety/TFAA.pdf)

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	All 12 posts		Subject: A 'regenerable' Friedel-Crafts acylation catalyst		Please login to post		Down


		bottleneck (Hive Bee) 02-01-03 19:52 No 403374				A 'regenerable' Friedel-Crafts acylation catalyst
						While searching for possible protective functions for tryptophan for use in intramolecular acylation as a possible precursor to LSD, I came across the reaction at http://www.ul.ie/~ces/ts.html under the title "Clean Chemistry Alternative to Friedel-Crafts Acylation." The carboxylic reagent is the carboxylic acid itself (i.e., no previous derivatization required), by means of mixed anhydride formation with trifluoroacetic anhydride. Only catalytic amounts of polyphosphoric acid are used, so although the phosphoric acid can't be regenerated, not much is lost in the process. The "activating agent" for the phosphoric acid+mixed anhydride is also trifluoroacetic anhydride. It is used in amounts stoichiometric to the product, but after combination with the phosphoric acid and acylation of the intended aromatic substrace, trifluoroacetic acid results almost quantitatively (excepting the trace amounts bonded with the phosphoric acid). The trifluoroacetic acid is subsequently isolated and dehydrated back to trifluoroacetic anhydride. Presumably quite a few catalysts for the dehydration of TFA to TFAA must exist? In any event, it wouldn't hurt to have a peek at those references I guess...



		Organikum (Hive Addict) 02-02-03 05:17 No 403504				trifluoroacetic
						Trifluoroacetic acid - i am after this for some time as it is not realy OTC and also not so easy to make if you don´t sit on a big stash of teflon and love to do pyrolysis at >550°C..... And you want to convert this to the anhydride? Also my usual chem supplier (not supply house, more private) was not very pleased also he promised to do his best. If I had asked him for the anhydride.... Polverone wanted to bring something up with high voltage discharge, but I am not sure if he did already. Somebody with 5 liters TFAA to much around here? Acid is ok, would take the anhydride too.... buhuu <whine> buhuu.... ORG nothing special



		bottleneck (Hive Bee) 02-02-03 11:56 No 403570				>Trifluoroacetic acid - i am after this for
						>Trifluoroacetic acid - i am after this for some time as it is not realy OTC I guess that would be true most places in the world. I am not really suggesting this as an OTC prep, but if someone had producion of industrial quantities in mind, maybe it deserves a second look. > And you want to convert this to the anhydride? Indeed. Would that be difficult? I thought there were many reagents to do this, but if nothing else works, surely dropping thionyl chloride in TFA will form TFAA? There are a couple of methods of producing TFAA from TFA described in US6248923 (Process for the production of fluorocarboxylic acid anhydrides), like reacting with halo, di-halo or tri-haloacetic acid.



		Organikum (Hive Addict) 02-03-03 02:49 No 403819				you are right bottleneck
						The ketenelamp works here also for TFAA from TFA. My mistake I overlooked this in my emphasis concerning the bad availabilty of TFA. Thanks for the patent so. ORG nothing special



		Rhodium (Chief Bee) 07-30-03 02:40 No 450648				Regenerable Friedel-Crafts acylation catalyst (Rated as: excellent)
						Full article, retrieved by Kinetic: Toward a Clean Alternative to Friedel-Crafts Acylation: In Situ Formation, Observation, and Reaction of an Acyl Bis(trifluoroacetyl)phosphate and Related Structures J. Org. Chem. 63, 8946-8951 (1988) (https://www.rhodium.ws/pdf/f-c.acylation.clean.alternative.pdf) It goes on to say that you can dehydrate TFA to TFAA using P₂O₅ on a laboratory scale, with no further details given. Anyone got a lab procedure? Or is it just to mix (carefully add oxide to acid) and distill? I wonder if you could use this method with alanine as the acid (which would form N-TFA-alanine in situ)? If so, then after a workup including treating the formed N-TFA-cathinone with a mild base, you would end up with a (substituted) cathinone in one pot! Starting with N-methyl-alanine would of course give methcathinones similarly...



		lugh (Moderator) 08-05-03 21:25 No 451889				Lab Procedure
						The laboratory distillation procedure was published by JM Tedder in Chemical Reviews 55, 787-827 1955 Chemistry is our Covalent Bond



		Aurelius (Active Asperger Archivist) 08-05-03 22:54 No 451906				Lugh
						How do you come up with this stuff? That's either one hell of a search database you've got or an even better memory! And if you've got the ref, why not post the procedure? Act quickly or not at all.



		lugh (Moderator) 08-05-03 23:17 No 451911				Time
						There wasn't time to fetch the reference, perhaps some other bee can find it Chemistry is our Covalent Bond



		mentallyill (Stranger) 09-06-03 00:57 No 457401				TFA From trichloroacetic acid???
						SWIM is also interested in producing TFA/TFAA. SWIM is curious about a halogen displacement reaction between trichloroacetic acid and a possible chemical such as aluminumfluoride. It seems possible that a displacement between the fluorine and the chloride should take place leaving trifluoroacetic acid and aluminum chloride. Any insight on this thought? runs with scissors



		Vitus_Verdegast (Hive Bee) 09-06-03 02:52 No 457409				preparation of trifluoroacetic acid (Rated as: good read)
						Couldn't find any refs on a possible halogen displacement reaction the way you suggest. Found this ref on preparation by halogen exchange : Improved preparation of trifluoroacetic acid. Henne, Albert L.; Trott, Paul. Ohio State Univ., Columbus, Journal of the American Chemical Society (1947), 69 1820. CODEN: JACSAT ISSN: 0002-7863. Journal language unavailable. CAN 41:30998 AN 1947:30998 CAPLUS Abstract cf. C.A. 39, 3253.8. Details are given of the prepn. of SbF3Cl2 from SbF3 and of its reaction with com. (CCl:CCl2)2 to give 95% crude (:CClCF3)2;oxidation with alk. KMnO4 gives 87% F3CCO2H. If you have the necessary skills to handle anhydrous HF you might consider this. Another downside is the bad yield: Preparation of trifluoroacetic acid by the electrochemical fluorination. Kojima, Rimpei; Hayashi, Teiichi; Takagi, Shushi. Govt. Ind. Research Inst., Nagoya, Japan. Nagoya Kogyo Gijutsu Shikensho Hokoku (1960), 9 516-22. CODEN: NKGSAR ISSN: 0027-7614. Journal language unavailable. CAN 55:12956 AN 1961:12956 CAPLUS Abstract CF3CO2H (I) was prepd. by the electrolysis of glacial AcOH, Ac2O, Me2CO, or AcCl in anhyd. HF. Under the following conditions I was obtained in the highest yield by the electrolysis of 40.5 g. Ac2O and 23.5 g. Me2CO in 800 ml. anhyd. HF: current d. 2.3 and 2.8 amp./sq. dm.; total current 139 and 139 amp.-hrs.; current efficiency 10 and 9%. The yield of I was 22 and 20%, resp. In the case of glacial AcOH, by applying reversed current periodically at the interval of a few sec., the current efficiency was improved. A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/dreamw.html)



		Rhodium (Chief Bee) 09-21-03 01:30 No 460168				Preparation of Trifluoroacetic Anhydride (Rated as: excellent)
						The Use Of Trifluoroacetic Anhydride And Related Compounds In Organic Syntheses J. M. Tedder Chem. Rev. 55, 787-827 (1955) (https://www.rhodium.ws/pdf/trifluoroacetic.anhydride.pdf) Preparation of Trifluoroacetic Anhydride (p. 821-822) Swarts originally prepared trifluoroacetic anhydride by distilling the acid over phosphoric anhydride¹⁹³ and this remains the most convenient method of preparation for use in the laboratory. The anhydride can also be prepared by treating the acid with stabilized sulfur trioxide⁷⁷, but this method is not well suited to small-scale laboratory preparation. Because sulfur trioxide boils very close to the boiling point of trifluoroacetic anhydride [SO₃, bp 44.6°C; (CF₃CO)₂O, bp 39-40°C] it is necessary to use a slight excess of the acid. The use of sulfur trioxide comes into its own for large-scale preparations where the relative costs of phosphoric oxide and sulfur trioxide are important. Trifluoroacetic anhydride is a volatile liquid which, unlike the acid, does not fume extensively in air. Because the material is so volatile and hygroscopic, it is usually best prepared directly from the acid as and when required. Like trifluoroacetic acid the anhydride can be stored in glass vessels, but it attacks rubber, cork, and most common metals. References {77} Patent US2628253 {193} Swarts, F., Bull. Acad. Roy. Belg. 8, 343 (1922)



		Rhodium (Chief Bee) 10-07-03 19:16 No 463239				Lab Prep of Trifluoroacetic Anhydride (Rated as: excellent)
						Sur l'acide trifluoroacétique F. Swarts Bulletin de l'Académie royale de Belgique (Classe des Sciences) 8, 343-370 (1922) Abstract Preparation of trifluoroacetic anhydride by dehydration of the corresponding acid using P₂O₅. (Article freely translated from French by Rhodium) In a distillation setup with the recieving flask submerged in a dry ice/ether mixture, 40g of P₂O₅ was placed in the distillation flask, and 16g of trifluoroacetic acid was slowly added with the aid of an addition funnel. There was no significant rise in temperature. After allowing the mixture to stand for one hour, the flask was heated to 100°C (bath temp), whereupon a relatively rapid distillation commenced, without any signs of decomposition. The distillate solidified in the reciever. It was then fractionately distilled through a short vigreaux column, care being taken to protect the liquid from atmospheric moisture, by heating gently on a water bath. The pure anhydride distilled between 39.5-40°C (corr.), again collected in a recieving flask cooled in a dry ice/ether mixture, where it solidified, mp -65°C. By vapor density measurement, it was determined that the distillate contained no trifluoroacetic acid. Compare with the preparation of Trifluoroacetyl Triflate in Org. Syn. Coll. Vol. 7, p. 506 (http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?rxntypeid=2&prep=CV7P0506) Also read the Trifluoroacetic Anhydride MSDS (http://www.halocarbon.com/safety/TFAA.pdf)

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