mario840 posted a reference to an article detailing the synthesis of phenylacetones via arylation of acetylacetone, which was promptly detritused due
to street-slang (I suppose): https://www.sciencemadness.org/whisper/viewthread.php?tid=16...
I was aware of that article and think it is of general interest, but didn't want to post before I could report some experimental details.
The reference (copied from mario840's post):
Copper Catalyzed Arylation/C-C Bond Activation: An Approach Toward alpha-Aryl Ketones by Chuan He, Sheng Guo, Li Huang, and Aiwen Lei J. Am. Chem.
Soc. vol 132, No. 24, 2010
One thing the authors fail to mention (unless I overread it) is that a very similar arylation of acetyl acetone has been performed before: Chemistry
Letters 597-600 (1982) http://www.erowid.org/archive/rhodium/chemistry/p2p.acetylac...
The difference is mainly the solvent (DMSO vs. DMF), the in-situ generated potassium salt of acetylacetone, vs direct usage of the potassium salt and
the addition of water of crystallisation of K3PO4.3H2O. In any case, it doesn't cast a good light on the referees.
I can confirm that the 1982 method works and got consistent yields in the 50% range with reduced solvent volume.
One thing that is unclear to me is if the authors of the 2010 paper really used K3PO4 or rather K2HPO4. On one hand I guess a strong base is needed to
deprotonate acetylacetone, on the other hand commercial "potassium phosphate trihydrate" tends to be K2HPO4.3H2O. I've seen too many papers
originating from China misreporting the used chemicals, that I am somewhat weary. I guess only small scale experiments will tell.
The other point of interest is - of course - compatibility with alkoxy substituents. Also here only experimentation will tell.
PS: This is certainly not a commercially viable method for underground production of amphetamines, but it may be very well suited for small-scale
amateurs.turd - 2-6-2011 at 21:55
K2HPO4.3H2O does not do it - in a 3g experiment I got mostly unchanged PhBr and some solids, which I didn't analyze more closely. And frankly, I'm too
lazy to make K3PO4, which I fear is not completely trivial. smuv - 2-6-2011 at 22:02
Interesting.
As one bitter reviewer once put it, before palladium cross couplings, there was copper chemistry.
K2HPO4.3H2O does not do it - in a 3g experiment I got mostly unchanged PhBr (...)
I would use Na2CO3 or K2CO3 + small amout of water. As they claim, water is important in this reaction.
K3PO4 is similar to these carbonates, K2HPO4 is not because hydrolysis PO4 anion is larger than HPO4 anion.
BTW
in this article they also give some results in DMF as solvent and effects are very similar to DMSO.Currently I do not have DMSO, but I have some DMF.
I will try this if I have time (also with PhBr). turd - 3-6-2011 at 03:48
Another alternative is quite possibly the use of equimolar amounts of K(acac) (trivially made with good purity, as opposed to K3AsO4) and K2HPO4.3H2O.
When I have time (not soon ) I might try that.Gualterio_Malatesta - 5-6-2011 at 03:22
Hey ya, turd!
Do you use commercial acetylacetone or do you prepare it via sodium ethoxide method?
If latter, could you please describe the preparation of acetylacetone in details based on your personal experience.
Thanks. turd - 8-7-2011 at 13:47
Quote:
Do you use commercial acetylacetone or do you prepare it via sodium ethoxide method?
Commercial of course - cheap, plentiful, unwatched.
Made a quick experiment with 1 eq. PhBr, 3 eq. K(acac), 3 eq. K2HPO4.3H2O, 0.1 eq CuI, DMSO, 20h@110°. Two points of interest:
1) it works (though isolated yield was mediocre)
2) during workup goodly amounts of a black/dark blue powder which was identified as Cu(acac)2 and a very fine orange powder of unknown composition
(Cu?) was isolated.
So far the phenylacetic acid/ethyl acetate/acetic anhydride process seems much nicer for plain phenylacetone (P2P), but this procedure might have
some merit for substituted P2Ps.jon - 8-7-2011 at 14:33
hey turd
in the dakin west reaction, does sodium acetate work as a catalyst or does it have to be pyridine? turd - 8-7-2011 at 14:55
Sodium acetate works quite nicely. A large excess of acetic anhydride and fused sodium acetate is the key. Most of the acetic anhydride is recovered
and sodium acetate is dirt cheap. No need for that stinker pyridine. If you're interested in Dakin-West and don't know it already, check out: https://www.sciencemadness.org/whisper/viewthread.php?tid=85...jon - 8-7-2011 at 16:11
i'm familiar with it.
it's an alltime favorate.solo - 1-9-2011 at 06:50
Reference Information
Copper Catalyzed Arylation/C−C Bond Activation: An Approach toward α-Aryl Ketones
Chuan He, Sheng Guo, Li Huang and Aiwen Lei
J. Am. Chem. Soc.
2010, 132 (24), pp 8273–8275
DOI: 10.1021/ja1033777
) I might try that.