Here's an idea. Take a propiophenone, ArCOCH2Me, and halogenate it. As Rhodium showed me in a previous thread, it will halogenate next to the carbonyl. It can only halogenate at the methylene group, as the other group on the carbonyl is the aromatic ring, and will not undergo addition at that carbon.
So now you have ArCOCHXMe. Reduce the ketone to an alcohol, and then dehydrate the alcohol with a hydrogensulfate to the alkene: ArCH=CXMe.
Reaction of the halogen with a base such as hydroxide, or an amide, MOH or MNH2, would yield the enol ArC=C(OH)Me, which would tautomerize to the ketone ArCH2(CO)Me, which is of course a phenylacetone.
Alternatively, if a metallic amide was used, the enamine would tautomerize to the imine, which could easily be hydrolyzed to the ketone, or reduced if desired.
I got the idea as an extrapolation on the following text, so if my version will not work, then perhaps this is something to think about.
"Ketones, carboxylic esters (including lactones), and amides (including lactams) can be sulfenylated at the
alpha position by conversion to the enolate ion with a base such as lithium N-isopropylcyclohexylamide and treatment of this with a disulphide. The reaction involves nucleophillic substitution at sulfur.
* * *
The
alpha sulfenyl carbonyl compounds prepared by this reaction can be converted to
alpha,
beta-unsaturated carbonyl compounds (
by reduction of the carbonyl to the alcohol, followed by dehydration, according to the picture scheme) The sulfenylation reaction has also been used as a key step in a sequence for moving the position of a carbonyl group to an adjacent carbon."
Then it shows the following, but as structural pictures, not text:
RCOCH2Me --> RCOCH(SPh)Me --> RCH(OH)CH(SPh)Me --> RCH=C(SPh)Me --> RCH2COMe
This effectively moves the carbonyl group one position in either direction that it is possible, determined by which side the sulfenyl group adds onto. In propiophenone, the only side it can add onto is the one and only
alpha carbon, the middle methylene group of the aliphatic chain. This would of course reposition the carbonyl at this position, effectively transforming propiophenone into phenylacetone.
It cites OrgSyn
VI, 23, 109; 688 for this specific concept, but I am unable to locate this entry on
http://www.orgsyn.org
I really think it is there, I am just being a retard and cannot find it with my queries. If someone could provide a link to that paper here, I'd be very thankful.
It sounds like this procedure is meant to be done in one pot, which would make for a cool P2P synthesis from propiophenone. This is better than synthing propenylbenzenes from propiophenones in my opinion. You are that much closer to the final product.
PrimoPyro
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