@Doucherman, have you seen this?

Synthesis, Crystal Structure and Bioactivity of N-Phenethyl-4-hydroxy-4-phenyl Piperidine Hydrochloride
WANG Hai-Feng XUE Si-Jia? ZHU Jun YANG Ding-Rong JIN Jia FANG Zhi-Kun
Vol. 28, No. 6
2009. 6 Chinese J. Struct. Chem. 742~746
http://jghx.fjirsm.ac.cn/jghx/2009No6/617-3621.pdf

"1-Phenethyl-4-piperidone
(a) A solution of phenethylamine (2.42 g) in 2 mL methanol is added dropwise with stirring to another solution of methyl acrylate (6.88 g) in 3 mL methanol, and then stirred for 30 min at room temperature. The reaction mixture was heated under reflux for 8 h, followed by concentration in vacuo on a rotary evaporator. The yellow oil residue was compound 1 (5.53 g, yield 94.4%).

(b) A mixture of 0.2 mL dry methanol and 4.40 g compound 1 in 15 mL dry toluene is added dropwise with stirring to a stirred solution of 0.42 g sodium in 20 mL dry toluene, which was refluxed for 6 h and then cooled to room temperature. The mixture was extracted with 15 mL hydrochloric acid twice, heated under reflux for 6 h, and then cooled to 0?10 °C. 35% Sodium hydroxide was added dropwise with stirring to adjust the pH value to 8.5, followed by extraction with 15 mL× 3 ethyl acetate. After being washed with 20 mL× 3 concentrated salt solution and dried with MgSO4, the resulting mixture was concentrated in vacuo. The yellow solid residue was 2.20 g of 2, yield 72.3%."

If the sodium could be replaced by lithium it would make that synth much nicer, the phenethylamine could be obtained through decarboxylation of phenylalanine. The wiki for methyl acrylate states it is used in the synthesis of remifentanil so is common knowledge and may be somewhat watched.

sounds intersting although i'd love to see a reference or possible mechanism for the cyclization i can't figure out exactly how thatwould work

looks like a mannich scheme of some sort.

sounds intersting although i'd love to see a reference or possible mechanism for the cyclization i can't figure out exactly how thatwould work

looks like a mannich scheme of some sort.

As I understand it, the mechanism is two mannich reactions in a row. The product would need to be decarboxylated to get to the ketone.

The reaction itself might be tricky in practice, because of the possibility of an imine also forming on the b-oxoglutaric ester. Perhaps those issues could be avoided by careful addition of the reagents.

Also someone should fix the wiki if they have access, as the wiki for methyl acrylate states it is used as a reagent in the synthesis of remifentanil. Which is false ethyl acrylate is acually used in a Micheal addition with the nitrogen of the piperidine and ethyl acrylate. Someone should get it removed before methyl acrylate gets a bad name, their ethyl acrylate page contains no reference to remifentanil! Having a quick look, it is definitely obtainable OTC!

edit; It is actually methyl acrylate used, I was quoting out of STRATEGIES FOR ORGANIC DRUG SYNTHESIS AND DESIGN by Lednicer, and the fentanyl section especially has several notable errors that being one. I did not think remifentanil had an ethyl ester, but double checked that book before posting. Then looking over the structure at wiki ect states it is a methyl ester, which it is. He also gives the structure for fentanyl and calls it ocfentanil among others.

acrolein, a very nasty chemical, is the aldehyde of the acrylic acid is produced by the dehydration of glycerol or reaction with strong acid. That might be usable, if one can oxidize it selectively to yield acrylic acid, or do some sort of rearrangement to form an ester, salt, etc...

@Jon,

The Preparation of Some Piperidine Derivatives by the Mannich Reaction
BY C. R. NOLLERAN D V. BALIAH
http://127.0.0.1/Naf1/4-piperidones-one-pot-1.pdf

I'm not particularly familiar with the mechanism of the reaction, but it looks like the ketone has to have at least one secondary carbon, which is why you wanted to use glutaric acid because then you can just decarboxylate the product to get n-phenethylpiperidone.  Am I understanding correctly?

You need an electron withdrawing group on either side of the acetone (eg, glutaric acid or one of its esters) to make the alpha protons acidic, and therefor make enol formation favorable.

Alright, that makes a lot of sense actually.  This sounds a lot better overall than pumping acrylic acid or acrolein vapor through homemade equipment.

^ Yes, that's the one he's talking about; he posted a this link previously.

He posted it in the 'routes to fentanyls' thread.