06-06-04 20:06
No 511809
Well, bees, here's one I need some help on. It's so unlikely to work that I dare not post it as a plausible route to P2P, but nonetheless I can't find out why it wouldn't work either! So maybe one of you can educate me!
Basic premise: One-pot chlorination of acetone and subsequent alkylation of benzene or activated aromatic.
Chlorination of acetone is an acid-catalyzed process. And alkylation of aromatics with haloacetones is a tempting one-step method to phenyl-2-propanones of all sorts. Raining on the parade is the fact that chloroacetone is no fun to deal with--to make, store, purify, and use. So I had this idea.
Imagine an aromatic that was activated enough to be substituted under relatively mild conditions. Mix it with acetone, some sort of FC catalyst (ZnCl2 comes to mind) and catalytic amounts of HCl. Add some sort of oxidizing influence and the following reactions should occur:
2 HCl + {O} --> Cl2
Acetone + HCl (+ ZnCl2?) --> Acetone Enol, + Cl2 --> ClCH2Ac + HCl
ClCH2Ac + Ph-H + ZnCl2 --> Ph-CH2Ac + HCl
As long as the oxidizing agent wasn't strong enough to mess up ketones like acetone, or react with the lewis acid (ZnCl2), it would be rather invisible.
Air comes to mind in this regard, perhaps with some sort of catalyst. A Copper salt, perhaps? Or maybe FeCl2 could be used as both lewis acid and oxidation catalyst...
KMnO4 also might work. MnO2 certainly would, but would consume HCl as it was converted to MnCl2. All of them would generate water, and this might screw up the lewis acid. Perhaps sulfuric acid or some drying agent could be added.
If the aromatic is activated enough that anhydrous conditions aren't necessary, things become much simpler. Electrolytic oxidation is then probably the method of choice. Bleach might also work.
Finally, for one not afraid of large amounts of HCl, anhydrous conditions, some zinc or iron metal, acetone and perhaps ligroin or other nonaromatic hydrocarbon solvent, a touch of HCl, and the careful addition of TCCA in acetone would likely do the job. Use of a dropping funnel and rapid stirring is a must. The TCCA would supply both chlorine and oxidation. Addition must be slow enough to keep the quantity of free chlorine low, so that there is little polychlorination of the acetone. 6 HCl will be generated for every mole of TCCA consumed.
Free-radical inhibitors like BHA, BHT, or hydroquinone would probably boost yield, since there are no free-radical pathways of desire here.
We'll all meet someday...on the other side
(Wonderful Personality)
06-07-04 01:02
No 511848
In situ chlorination of acetone - nice idea I thought about this lately myself but...
- chlorine in any form and a Lewis acid will chlorinate the ring of the benzene
- will not ZnCl2/HCl and acetone yield ethylchloride? EtOH and ZnCl/HCl does....
- ZnCl2 is to weak for FC alkylations on non-substituted benzene as far as I know. AlCl3 works, SnCl4 may work as FeCl3. FeCl2 wont.
- and I fear ZnCl2 will facilate quick autocondensation of the acetone - holy polymeres - this problem is also seen by the usual AlCl3 catalyzed chloroacetone - benzene FC-reaction.
I dont say there might not be a way - perhaps.
What way? No, no. Much to early to talk about.
Anyways, I believe there got something mixed up - Friedel-Crafts and oxidative coupling aŽla Mn(III)acetate in one pot and heavy (overhead!) stirring applied....
- voilaŽ! - arylketones hopping out of the flask like white rabbits out of the magicians cylinderhat! 
ORG
(Hive Bee)
06-12-04 20:36
No 513014
i recall reading someplace that ultraviolet light could form a *ch2coch3 radical from acetone which could then attach to a phenyl substrate.
(Chief Bee)
06-13-04 00:14
No 513039
The role of the Mn3+ in the following porocedure is simply to generate acetonyl radicals: Phenyl-2-Propanones: Mn(III)-Catalyzed Aromatic Acetonylation (../rhodium /p2p.ma
It also seems somewhat related to the UV-catalyzed acetone enolate acetonylation: Post 485886 (Rhodium: "More goodies for the enolate curious", Chemistry Discourse)
The Hive - Clandestine Chemists Without Borders
(Hive Bee)
06-13-04 11:55
No 513120
Would reacting KMnO4 by slowly adding it to a mixture of Glacial Acetic Acid, Acetic Anhydride, and Absolute Ethanol work for producing the required Mn(OAc)3
I am not sure my reasoning is sound and I don't currently have the required Acetic Anhydride (Would it be necessary)?
My thoughts were along the lines of the ethanol being oxidized straight to acetic acid with the acetic anhydride removing any water formed and creating more acetic acid.
The acetic acid reacting with the potassium ions to form potassium acetate and the manganese ions reacting with the acetic acid to produce Mn(OAc)3 and again the acetic anhydride removing any water formed.
The acetic anhydride might not be necessary but I think the reasoning is ok. Would the potassium acetate be a reaction poison for the P2P? Or would it drive the products in a different direction? If the acetic anhydride isn't necessary this could be a moderately OTC route to P2P.
The article indicated that it should be possible to regenerate the Mn(OAc)3 in situ by adding KMnO4 to the reaction mixture so I assume the KOAc is not a reaction poison.
My other question is how much water can the benzene/acetone reaction tolerate?
(Chief Bee)
06-13-04 14:16
No 513127
I am not sure my reasoning is sound and I don't currently have the required Acetic Anhydride (Would it be necessary)?
No acetic anhydride is used in the procedure, only acetic acid is necessary, together with KMnO4 and a Mn2+ salt (can be made from KMnO4 and hexamine) and some common salts. Read this for a detailed procedure: Preparation of Manganese(III) acetate (../rhodium /mangan
Your other questions are rather disorganized, and you should UTFSE on this topic to further your knowledge about the reaction.
The Hive - Clandestine Chemists Without Borders
(Hive Bee)
06-13-04 19:00
No 513165
Sorry if my questions didn't quite make sense chief.
Its the drugs the doctor perscribed.
I looked over the rhodium archives about Mn(OAc)3 production and did some searching and hadn't found complete answers yet.
What I really wanted to know is if a one-pot reaction from KMnO4, acetic acid, and ethanol can produce Mn(OAc)3 (with or without Acetic Anhydride)? This could then be mixed with Benzene and Acetone to form the P2P.
The short answer is that it will work (with or without the acetic anhydride). The long answer was there is a better way to do it. Starting with MnO2 and combining with H2O2 and acetic acid in water. The Mn(OAc)2 is then recovered and the Mn+3 formed as per the rhodium archives by reacting in GAA with KMnO4. Since the solution is acetic acid it could be directly added to the Benzene and Acetone to give the desired product. The patent literature also suggests that the oxidation reaction is not very sensitive to water.
Some notes I found in patent literature were:
1) Acetic Anhydride speeds up the formation of the +3 salt as well as the oxidation reaction. Possibly because it removes water?
2) Potassium Acetate supposedly inhibits side reactions.
3) The second major product is phenyl acetic acid.
Of course the compounds in 1,2, and 3 also react to form the desired product but that reaction is more sensitive to water.