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Author: Subject: Carboxylic acid -> Alkan
nightflight
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[*] posted on 18-3-2007 at 07:00
Carboxylic acid -> Alkan


Hi,

I was intersted in how to perform this best, with not so expensive catalysts and good yields.

So what I cam came across to synthesize an alkane from a aninoaryl-CO2H was:

I. Reacting the carboxyclic acid with thionyl chloride to yield a
chlorocarboxylic acid.

II. Catalytic reduction of halide to yield a hydrogen, resp. aldehyde (Aluminiumamalgam?)

II. Clemmens reduction of the Aldehyde to get the alkane, by heating with Zn(Hg) in HCL.

What do you think about the Barton decarboxylation mentioned in this paper: http://www.chem.harvard.edu/groups/myers/handouts/1_Reductio...
?
Reacting an ester of N-hydroxy-2-thiopyridine with a tin-hydride catalyst -unfortunately not much is stated about the selectivity of this decarboylation.

Intresting would be Vogel´s synthsis of (S)-2-Amino-3-phenylpropan-1-ol, by reaction phenylalanine to the ethylester*hcl in EtOH and SOCL2 successive reduction in high yield by Sodiumborohydride and subsequent deoxygenation of the alcohol, by the Mitsunobu displacement, wouldn´t it?

[Edited on 18-3-2007 by nightflight]
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[*] posted on 18-3-2007 at 07:17


Caboxylic acid to the alkane can be done directly in one step with red P and hydroiodic acid. Look in the old Gattermann (Sciencemadness library), theres a preparation of diphenylmethane from benzophenone in there that uses this method. It is stated there that HI/P reduces all oxygen compounds like alcohols, aldehydes and carboxylic acids, to the alkane.

[Edited on 18-3-2007 by garage chemist]




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[*] posted on 18-3-2007 at 07:33


Oh cool, thanks I ´ll look that up, after like spending 3 days of searching and learning the above mentioned stuff.;)

[Edited on 18-3-2007 by nightflight]
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[*] posted on 18-3-2007 at 08:10


Quote:
Originally posted by garage chemist
Caboxylic acid to the alkane can be done directly in one step with red P and hydroiodic acid. Look in the old Vogel (Sciencemadness library), theres a preparation of diphenylmethane from benzophenone in there that uses this method. It is stated there that HI/P reduces all oxygen compounds like alcohols, aldehydes and carboxylic acids, to the alkane.


I apologize for my question but I wasn't able to locate the preparation of diphenylmethane using the RP/HI......would it be possible to give the page #....thanks,......solo




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[*] posted on 18-3-2007 at 08:10


But why is it so hard to find? all I see is reductions to alcohol, using various metal catalysts or the hunsdiecker reaction using heavy metals in teh presence of Br and CCl4
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[*] posted on 18-3-2007 at 08:21


Oh, I didn't remember it correctly, it was not Vogel, it was Gattermann (the 1909 version) in which the HI/P reduction of benzophenone to diphenylmethane was described.

EDIT: Page 301 in the Gattermann from 1909. Also reduction of benzoic acid to toluene, stearic acid to octadecane, glycerol to propane etc. are stated as being possible with HI/P.

[Edited on 18-3-2007 by garage chemist]




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[*] posted on 18-3-2007 at 08:30


.. but that´s a ketone, not a carboxylic acid. Ok, Hi is expensive, but that wouldn´t be a reason to not mentioning it as it´d be an easy and important reaction.

edit: oh-ok cool -could you provide a link? :cool:

[Edited on 18-3-2007 by nightflight]
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[*] posted on 18-3-2007 at 08:33


It is clearly stated that the HI/P reaction works with all oxygen compounds, alcohols, aldehydes, carboxylic acids etc... Look it up!

Even unsaturated compounds can be converted to saturated ones by means of HI/P, like benzene ---> cyclohexane.

EDIT: OK, link: http://www.sciencemadness.org/library/books/the_practical_me...

[Edited on 18-3-2007 by garage chemist]




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[*] posted on 18-3-2007 at 08:57


thanks a lot!
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[*] posted on 18-3-2007 at 13:17


Quote:
Originally posted by garage chemist
It is clearly stated that the HI/P reaction works with all oxygen compounds, alcohols, aldehydes, carboxylic acids etc... Look it up!

Even unsaturated compounds can be converted to saturated ones by means of HI/P, like benzene ---> cyclohexane.

EDIT: OK, link: http://www.sciencemadness.org/library/books/the_practical_me...

[Edited on 18-3-2007 by garage chemist]


I did find the reaction on page 301 as stated, but have looked for the statement, where the author makes the statement you quoted......I'm not lazy perhaps a bit farsighted, so how about giving up the page of the 1907 publication where the information is posted.......solo




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[*] posted on 18-3-2007 at 14:45


This all depends on what exactly you are trying to decarboxylate. I assume that the COOH is not attached to the ring, nor are groups that would cause problems. Don't count on the Hunsdieker to give good yields on aromatic cpds.

The HI/RP is in the older editions as well, but not the newer ones. The reference given is available at Gallica, and mentions some of the other reductions. What Gattermann says says nothing of the yield or conditions necessary in reduction of acids on a preparative scale - these are hot sealed glass tube methods (with pressure from gas evolution as well as vapor pressure), and acids are not likely to reduce quite as easily as benzophenone.

[Edited on 18-3-2007 by S.C. Wack]
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[*] posted on 19-3-2007 at 01:47


What do you all think of the steps proposed in the entry post?

And how about using Al(Hg) in the Rosemund reduction -alternatively Palladiumchloride is available -the over reduction would be a good thing in this case.
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[*] posted on 19-3-2007 at 07:00


Well since you asked, one I would react the COOH with some NaBH4 and NiCl in water at RT to get the OH then use the Hypo/I2 to reduce the OH to the CH3........solo



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[*] posted on 20-3-2007 at 06:39


...that came to my mind yesterday night after reading Vogels synthesis of 2-amino-3-phenylpropan-1-ol.
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[*] posted on 24-3-2007 at 17:37


Quote:
Originally posted by solo
Well since you asked, one I would react the COOH with some NaBH4 and NiCl in water at RT to get the OH then use the Hypo/I2 to reduce the OH to the CH3........solo

In fact it´s the PI3 that forms the alkyliodid, which then has to be reduced to yield the alkane.

So I´m now at this point, since HI redeuction needs pressure to yield 150°C and I don´t know how to perform it:

-esterification (already done with n-butanol, to provide a good leaving group and it was dry and readily available),
reduction with Al(Hg) to -hopefully- yield the alcohol,

-synthesis of the alkylhalide with 1/3P&I -> CH2I + H2PO3

-reduction with Al(Hg) getting the alkane.

Could anybody expalin how after this document: http://www.geocities.com/nepalorganic/co_acid.htm

an Alkane can be made with Grignard reagents? Is this the reaction wheere cooling to -70°C is necessary as for the gereartion of carboxyli acids by Grignard? -sorry, did´t yet find that much on it.

[Edited on 25-3-2007 by nightflight]
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[*] posted on 24-3-2007 at 21:07


Quote:

Could anybody expalin how after this document: http://www.geocities.com/nepalorganic/co_acid.htm

an Alkane can be made with Grignard reagents? Is this the reaction wheere cooling to -70°C is necessary as for the gereartion of carboxyli acids by Grignard? -sorry, did´t yet find that much on it.


You mean the CO2 one? Works in part because the carboxylic acid salt is formed, which isn't very reactive, and in part because it is run cold.

Alkanes are made via Grignard using halides, not acids RX + R'MgX => R-R' + MgX2
acids are OK for making alcohols or sometimes ketones.

if you're starting with a carboxylic acid you need to get it to being a halide first, the route depends on where you start and what the target is.
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[*] posted on 25-3-2007 at 04:01


could a halide of a acid halide be swapped for an hydrogen by a grignard reagent, what is the most convenient way to do so, anyway?:D

I´m thinking about sealing it in a flask with a keck clamp and some wire or string and throwing it into the micro for convenient heating (mw doesn´t speed up ester cleavage so donßt I think it´ll speed up things here), to obtain 150°C, which doesn´t seem like too much pressure is needed to get to this temperature.;)

[Edited on 25-3-2007 by nightflight]
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[*] posted on 25-3-2007 at 05:20


Quote:
Originally posted by nightflight
could a halide of a acid halide be swapped for an hydrogen by a grignard reagent, what is the most convenient way to do so, anyway?:D


Yes, sort of. It makes a ketone, which can react with the Grignard to give a tertiary alcohol. In the bad old days it was more common to make the Grignard, then convert it to the corresponding organo-cadmium compound and react that with the acid halide, as the cadmium compound is less reactive. The minor problem with this is the high toxicity of cadmium and its compounds, and the tendency of the organic cadmium compounds to ignite when exposed to air, made more interesting by the ether used as a solvent. Severe burns plus cadmium poisoning were poor incentives for recruiting new chemists.

Quote:
I´m thinking about sealing it in a flask with a keck clamp and some wire or string and throwing it into the micro for convenient heating (mw doesn´t speed up ester cleavage so donßt I think it´ll speed up things here), to obtain 150°C, which doesn´t seem like too much pressure is needed to get to this temperature.;)


Almost 5 bar if using just plain water, as a baseline. You'll have to do digging to find out for the reaction mix you plan. Be interesting to see a wire wrapped flask in the microwave.

http://www.engineeringtoolbox.com/saturated-steam-properties...

Sealed tube runs use heavy walled tubing and put that inside steel pipe for tube failure containment. Sometimes water or some other liquid would be placed in the pipe was well, and it would be sealed - this to reduce the pressure differential on the glass tube. Care must be taken to correctly calculate the amount of liquid to use in order to prevent too little or too much pressure in the pipe.
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[*] posted on 29-3-2007 at 04:24


How convenient is a MV, when it can be heated in a secure shell in a reg. oven? ;-))

Just out of interest, could the reduction of the alcohol proced liek this:

RCH2X + 2HI + 2H3O* -> RCH3 + 2H2O + I2 ?

the I2 is then racted with the RP to regenerate the HI(aq):

3I2 + 2P + 6H2O -> 2PI3 + 6H2O -> 6HI + 2H3PO3

Theoretically it could be used less HI but with more time the rxn should go to completion, for the HI reg. is permanent, couldn´t it?

What would yo think about substituting this with the reduction in NaBH4 and F3CCO2H, price-wise ?

[Edited on 29-3-2007 by nightflight]
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[*] posted on 8-6-2007 at 10:19
Barton Vs. Kolbe Decarboxylation maybye...


they join forces....


Since Barton radical decarboxylation was found threw search engine here it seems the place to ask and post

Ive been looking for interesting things to sonicate these days and radical decraboxyaltion of phenylalanine seems rather promising for interest levels…

First:
http://www.osti.gov/energycitations/product.biblio.jsp?osti_...

The methyl radical yield rises sharply at very low concentrations of methanol…..

Methyl radicals if they are needed will form in the gas bubble and be ready to react with the bulk fluid medium at collapse. Kind of a Kolbe et al. type of promise…..

Depending on the reaction methyl radicals can add to thermally decraboxylating phenylalanine, or if one had the specialized reagents barton decarboxyalation produces R groups with the addition of a hydrogen ……
http://www.organic-chemistry.org/namedreactions/barton-decar...

but im pretty sure home school techniques can deliver a ester of phenylalanine that will produce the R group with out all the fancy fine sigmaaldrich specials…

http://www.springerlink.com/content/xh07j39423831367/
Under the action of peroxides or UV radiation mercuric alkanoates undergo initiated free-radical decarboxylation with formation of alkylmercury compounds.

Um I really don’t want to create methylmercury but it shows the trend

Other refs:
Radical Reactions in Organic Synthesis By Samir Z. Zard

Provided by google books

http://www.osti.gov/em52/1999projsum/54834.pdf
The acetylene then reacts with OH•to form methyl radicals and carbon monoxide
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[*] posted on 8-6-2007 at 23:53


Quote:
Originally posted by S.C. Wack
This all depends on what exactly you are trying to decarboxylate. I assume that the COOH is not attached to the ring, nor are groups that would cause problems. Don't count on the Hunsdieker to give good yields on aromatic cpds.

The HI/RP is in the older editions as well, but not the newer ones. The reference given is available at Gallica, and mentions some of the other reductions. What Gattermann says says nothing of the yield or conditions necessary in reduction of acids on a preparative scale - these are hot sealed glass tube methods (with pressure from gas evolution as well as vapor pressure), and acids are not likely to reduce quite as easily as benzophenone.

[Edited on 18-3-2007 by S.C. Wack]

I translated once this german article from the 30s for the HIVE where they reduced all this acids and stuff with HI....

The procedure was like this:
95% H3PO4 + NaI or KI + a small amount of red phosphorus
The use of the highly concentrated H3PO4 allows temperatures which are sufficient to reduce almost everything without the need of a pressure vessel.
The authors explicitly suggested this method for use on an industrial scale.

The older industrial methods were indeed using HI with conc. HCl as solvent in a pressure vessel, or HI in concentrantions up to 72% IIRC under pressure - nothing for the amateur.

As a laboratory method in special to reduce alcohols the GAA/iodine/red phosphorus reduction system was used, but in these times GAA and iodine were rather expensive and chemists were poor.

The yields of the H3PO4 method were always named as >80%, H3PO4 is rather cheap and easily concentrated from the 85% of trade to the 95% asked for by simple heating, NaI and KI are also no problem, just the red phosphorus might be for some a problem in these days of the meth madness.

There was also what SAM posted at the HIVE (times before he went insane) - a scanned page from an unnamed old book - where it was stated that HI rips out oxygen from virtually EVERY organic molecule, if reaction conditions are harsh enough it goes next for the nitrogen.
This might explain that reducing phenylalanine with HI is not trivial as the conditions needed to reduce the acid will be near to the conditions reducing the nitrogen. I guess in this reaction the conditions (in special temperature) have to be very well controlled and it will take some tinkering to get them well adjusted. Then the yields should be very high as basically always with HI reductions.

/ORG



[Edited on 9-6-2007 by Organikum]




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[*] posted on 9-6-2007 at 04:36
I think this maybe easy to work


Quote:
Originally posted by nightflight
But why is it so hard to find? all I see is reductions to alcohol, using various metal catalysts or the hunsdiecker reaction using heavy metals in teh presence of Br and CCl4


Hunsdiecker reaction have been improved currently. if you have a beta-unsaturated acid as your raw material. This paper may be help:
Tetrahedron 61 (2005) 637–642.
You can get beta-arylvinyl bromides in 1-2min with high yield. Then just a reductive reagent will be needed after it.




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[*] posted on 9-6-2007 at 08:27


Reference Information


Stereoselective synthesis of (E)-b-arylvinyl bromides by microwave-induced reaction of anti-3-aryl-2,3-dibromopropanoic acids using an AgOAc–AcOH system
Chunxiang Kuang,* Hisanori Senboku and Masao Tokuda
Tetrahedron 61 (2005) 637–642.





Abstract
(E)-b-Arylvinyl bromides were stereoselectively prepared in high yields by microwave irradiation of the corresponding anti-3aryl-2,3-dibromopropanoic acids in AcOH in the presence of AgOAc for 0.5–3.0 min.







[Edited on 9-6-2007 by solo]

Attachment: Stereoselective synthesis of (E)-b-arylvinyl bromides by microwave-induced reaction of anti-3-aryl-2,3 dibromopropanoic (210kB)
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[*] posted on 9-6-2007 at 16:48


Do you know this decarboxylation? I don't know their name.

R-COONa + NaOH + CaO + Heat => R-H + NaCO3

I have read that the aldehydes alpha-halogen they are oxidized easily to carboxilic acid. That yield has the reaction:?

Acetaldehyde + NaClO + H2O => acetic acid

or

EtOH + NaClO + HCl + H2O => acetic acid

[Edited on 10-6-2007 by Filemon]
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[*] posted on 10-6-2007 at 13:03


Quote:

Do you know this decarboxylation? I don't know their name.


Quote:

R-COONa + NaOH + CaO + Heat => R-H + NaCO3



well in chemistry anything can happen....
but where did the Calcium go
to a happy place?

i have been seeing that added bicarbonate facilitates decarboxylation...

So
i hold in my hand a 500 mg gelaitan capsule of L-Phenylalanine
i will separate the cellulose and Mg stearate as the only other listed ingredients.
i will add bicarbonate until a homogeneous mixture is had in water.
A catalytic amount of methanol will be added
the mixture will be sonified at 20 kHz and up to 150 Watts without temperature concerns.

i wonder the result....
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