How do I get it to 3-methylpiperidone?

The rules of the Vespiary state that you need to post a literature citation relevant to your thread     You need to do some research on your question instead of expecting someone to take their valuable time and figure it out for you    You need to realize that there are known routes to the compound already published like almost everything else that a newbee might post on such a web site  One known approach to synthesizing 3-piperidones is oxidative cyclization which is discussed in the attached article 

anhydrous citric acid and react it with diluted sulfuric acid to yield 1,3-acetonedicaboxylic acid.

Before we address this topic, please demonstrate that you are not a hopeless moron: what gas is released during this reaction? How, therefore, should it be performed?

You can't convert piperidone to 3-methyl-piperidone. That you would consider it tells me that you don't really know what you are doing.

i found this intesting
















 






And here is the Paul Rabe paper from Ann. in 1904.
 
The original Knoevenagel prep paper from 1894 is 100+ pages and 3.6 Mb so too large to post here. Anyone interested can find it in References if they want to read it, it is in a rar file on RS along with this Rabe paper.
 
For comparison here is the pertinent paragraph from the Org Syn prep of same compound:
 
"To 500 g. (3.85 moles) of freshly distilled ethyl acetoacetate in a 1-l. flask, set in ice and well cooled, are added 152 g. (2 moles) of 40 per cent aqueous formaldehyde solution and 20–25 drops of diethylamine. The flask and contents are kept cold for six hours and are then allowed to stand at room temperature for forty to forty-five hours. At the end of this time two layers are present, a lower oily layer and an upper aqueous layer. The layers are separated, and the aqueous layer is extracted with 50 cc. of ether. The ether solution is added to the oily layer, and the resulting solution is dried over 30 g. of calcium chloride. The ether is then removed by distillation on a steam bath. The residue, amounting to approximately 500 g., is diluted with an equal volume of alcohol and is thoroughly cooled in an ice bath. Ammonia is then passed into the mixture until the solution is saturated. This requires from four to eight hours, and during this time the flask is kept packed in ice. The ammoniacal alcoholic solution is allowed to stand at room temperature for forty to forty-five hours. Most of the alcohol is now evaporated; the residue is cooled, and the solid 1,4-dihydro-3,5-dicarbethoxy-2,6-dimethylpyridine is removed from the remaining alcohol on a suction filter. The dried ester melts at 175–180° and weighs 410–435 g. (84–89 per cent of the theoretical amount)."
 
It will be interesting to compare that to the procedures of Knoevenagel (1894) and Rabe (1904) while noting that the Org.Syn prep was authorored in the mid 1930s.

And while the rest of that prep is a good read it is entirely concerned with oxidizing the dihydropyridine to pyridine, saponifying the ester groups, and decarboxylating the compound to obtain lutidine. Not my target. I will be following the procedure in paragraph above, merely substituting methyl acetoacetate for ethyl, which, Klute reminds us, is a piece of cake.
 

[Edited on 24-10-2008 by Sauron]

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Sauron

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posted on 23-10-2008 at 21:05
 






I guess I ought to have a closer look at the Knoevenagel reaction, and reread the Katritzky paper on the mechanism of the Hantzsch dihydropyridine synthesis. I would like to know whether the 1:1 condensation product of acetoacetic ester and formaldehyde that he spotted by NMR is isolable.

I am pretty sure that the ARK mechanism applies only to the formal, 3-component Hantzsch. In fact it is pretty clear that procedures like the one in Org Syn are not precisely Hantzsch reactions at all, although they involve the same reagents and arrive at the same products, simply because they aren't 3-component reactions. I don't think this is splitting hairs.
 
I did have another go at ARK's mechanism paper and he does include the methylenebis-ethylacetoacetate in his master reaction scheme and obviously recognizes the complexities. Well, I really would not expect any less from Katritzky.
 
His experiments were using benzaldehyde not formaldehyde.
 
Below is theethyl 2-methyleneacetoacetate resulting from condensation of one equivalent acetoacetic ester and one equiv. formaldehyde. Just as clearly, we could call this ethyl 2-acetylacrylate.and expect it to be highly reactive and readily polymerizing. I am a little dubious about whether or not this can be isolated, except maybe in a cold trap. where the self-condensation can be retarded. But ARK's spectral evidence for in situ formation and role in reaction with ethyl 3-aminocrotonate is pretty compelling.
 
The ACS Formaldehyde monograph described methylenemalonic esters and methylenebis(malonic esters) and as anticipated these do polymerize on standing but not instantly, and are isolable and distillable. However, no mention is made of a methyleneacetoacetic ester, just the methylenebis compound. I will have to dig deeper.
 
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