New Electrosynthesis of P2P

[foxy2]

Check this patent out!  This synthesis seems pretty easy, if you have acetic anhydride.  The yeilds for substituted benzyl chlorides are not stellar, however they were able to get an 80% conversion of BzCl to P2P.

Synthesis of benzyl methyl ketone (phenylacetone) from benzyl chloride and acetic anhydride.

Patent US4629541

In these examples, the anode is made of magnesium or aluminium, the cathode of nickel the solvent is DMF (110 g) and the supporting electrolyte is tetrabutylammonium fluoroborate (2 g, i.e. 6 mmol).

After the electrolysis (2.2 faradays per mole of benzyl chloride), the remaining benzyl chloride, the toluene which is a byproduct of the reduction of benzyl chloride, and benzyl methyl ketone, both in free form and in the form of its enol acetate, are determined by GC in an aliquot portion.

After the DMF has been evaporated off and the residue has been hydrolysed with hot dilute HCl, benzyl methyl ketone is isolated by extraction with ether. Pure benzyl methyl ketone has been identified from its IR and NMR spectra, and its purity has been verified by GC.

Do Your Part To Win The War

[Rhodium]

And now also in HTML. Nice find!

https://www.thevespiary.org/rhodium/Rhodium/chemistry/p2p.electro.html

[PolytheneSam]

Post 174633 (missing)

(PolytheneSam: "Re: a SERIOUS discussion of Tolulene ---> Meth", Stimulants)

Post 227898

(PolytheneSam: "Re: P2P from benzylchloride / LiAc / Li", Novel Discourse)

[foxy2]

Sam
I could probably have guessed that you had posed this before. At least my post convinced Rhodium to put it on his site.

Do Your Part To Win The War

[Rhodium]

If you guys would bother to include an abstract together with your posted references to make it interesting enough, there is a much greater chance people will read it, and me reading it is a prerequisite for the article to end up on my page.

[Scooby_Doo]

Here's another ref on P2P production, but this time no acetic anhydride which is kinda handy.

"Ketones are obtained by the acylation of cathodically generated carbanions. The carbanions can be formed by the reduction of halogenoalkanes."

Chem Lett 1021 (1977)

Basically zapping (technical ehh) Benzyl chloride in MeCN with something called Et4NOTs

[Elementary]

From reading the patent would I be correct in thinking,
that the solvent could be acetonitrile instead of DMF ?
The anode could also be zinc, cathode could be graphite and that other chemicals such as alkali chlorides could be used as the supporting electrolyte ?

I know an everyday cell like that !!! A typical zinc chloride battery (dry cell), remove the electrolyte from the new battery and you have a ready made ketone cell complete with graphite cathode !


Umm, how interesting !!

[Rhodium]

Buy the cheapest 1.5 volt non-alkaline battery you can find, and it will be the correct one - a D cell preferably, the largest available. Open it, and the rod in the biddle is graphite, while the inner casing is zinc. The "filling" is MnO2/NH4Cl and the outer case is most likely steel/iron. Discard the outer case and the filling.

[Rhodium]

(Note: The major product, (E)-1-phenyl-2-acetoxypropene (P2P enol acetate), is quantitatively hydrolyzed to P2P by shaking with 5% aqueous NaOH)

Electroreductive Acylation of Benzyl Chlorides with Acid Anhydrides. Stereoselective Formation of (E)-Enol Esters from Benzyl Alkyl Ketones.
Ikuzo Nishiguchi, Tsuneo Oki, Tsuneaki Hirashima, and Jiro Shiokawa

Chemistry Letters 2005-2008 (1991)

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/p2p.electroreductive.acylation.html)

Abstract
Electroreduction of benzyl chlorides in the presence of acid anhydrides brought about stereoselective formation of (E)-enol esters of the corresponding benzyl alkyl ketones, the initial acylated products, in good to moderate yields.



In this study, we report a unique electroreductive acylation of benzyl chlorides (1) with aliphatic acid anhydrides (2) to give the (E)-enol esters (3) of the corresponding benzyl alkyl ketones (4) as the main product in satisfactory yields. The corresponding benzyl alkyl ketones (4) and benzyl esters (5) were obtained as the by-products in small amounts.

A typical procedure is as follows:

A solution of 20 g (0.067 mol) of tetraethylammonium p-toluenesulfonate in 80 ml of anhydrous N,N-dimethylformamide was placed in cathodic (64 ml) and anodic (16 ml) chambers of a divided cell separated with a cylindrical ceramic diaphragm, to which a lead-plate cathode and a carbon-rod anode were attached. To a catholyte was added 2.53 g (0.02 mol) of benzyl chloride (1a) and 20.4 g (0.20 mol) of acetic anhydride (2a). The mixture was electrolyzed with stirring at room temperature under constant current condition (current density: 15-10 mA/cm² ) until 4.0 F/mol of electricity has been charged. The usual work-up of the catholyte and the distillation of the product mixture gave 2.50 g of (E)-1-phenyl-2-acetoxypropene (3a) (yield 71%), along with benzyl methyl ketone (4a) and benzyl acetate (5a) in 2% and 5% yields, respectively.


Other Electroreductive Acylations of Benzyl Chloride with Acetic Anhydride:

Post 458776

(ning: "Electrosynth of Ketones From Halides/Anhydrides", Methods Discourse)

Post 241695

(foxy2: "New Electrosynthesis of P2P", Methods Discourse)

[DrLucifer]

Im surprised this thread hasnt received more attention!
These findings are absolutely fuckin marvellous, thanks for spurring a little discussion foxy2, swim is grinning uncontrollably. This venture into foreign territory has certainly paid for itself, thanks again guys.
Foxy i could kiss ya  

[Rhodium]

Synthesis of 1-Aryl-2-propanones by Electrochemical Arylation of ?-chloro Ketones
M. Durandetti, S. Sibille, J.-Y. Nédélec and J. Périchon

Synthetic Communications 24(2), 145-151 (1994)

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/p2p.electroarylation.haloketones.html)



Abstract
?-Arylated ketones were obtained in moderate to good yields by one-step electroreductive coupling of ?-chloroketones
and arylhalides in DMF and in the presence of a Al- or Zn-sacrificial anode and a catalytic amount of a nickel complex.

[Organikum]

But sadly on second sight.....
The experimental part shows the drawbacks:

the aromatic halides (10 mmol) were introduced into a one-compartment cell fitted with Al rod/nickel-sponge or Zn rod/carbon fiber as the anode/cathode set of electrodes (cathode area ~20 cm2). The ?-chloroketone was added constantly to the solution via a syringe pump at a rate of 0.5 ml/h

20cmxcm cathode on 10mmol substrate and additition od 0,5ml chloroketone per hour....
I doubt the practical worth of the procedure (not to talk about iodobenzene for best yields). But its nevertheless a highly interesting approach as all the Ni-couplings are.

[armageddon]