(Hive Addict)
10-23-04 02:18
No 537223
(Rated as: good read)
Patent DE944251
Example 2
A solution of 200 parts 1,5-pentanedial in 800 parts 3% sulfuric acid is added, over the course of 2 h, to a boiling solution of 1100 parts crystallized FeSO4 and 200 parts (NH4)2SO4 in 1500 parts water. Workup as in example 1 yields 82% pure pyridine.
workup as in example 1: rxn-mixture is made alkaline and the aromatic base is distilled off.
Pyridine from nicotinic acid, found at http://www.korbis-labor.de/experimente/c
1.5 g nicotinic acid and 2.5 g CaCO3, when heated to decarboxylation with a bunsen burner give 0.3 mL py. not worth the hassle, nicotinic acid is also quite expensive
There's also another really crappy method, that produces mainly picoline (methyl-pyridine), but it's the most simple way I've seen so far. The guy just gives a brief description of what he did, including the note of his intended future publication of a detailed write-up, when his research would be done; the world is still waiting for it to be published. Well, maybe picoline can substitute for pyridine in some reactions...
It's in J.prakt.chem., 45,1.1892;22. He let's the world know that you "just have to distill the right amounts of ammonium phosphate and glycerine at such a temperature, that the formed aromatic base can be distilled off, as it is formed." "using 500 g propanetriol the reaction can be done in 6-8 h" "yield of total bases is ~25% of the theoretical amount, based on the glycerine"
Conclusion: Py remains a pain in the ass to synth at home. But at least for the dealkylation of vanillin / ethyl vanillin there's methods that work w/o it :
Post 291912 (Antoncho: "Demethylation of vanillin.", Novel Discourse)
Post 351285 (6079_Smith_W_II: "JP10265428", Novel Discourse)
--psyloxy--
(Hive Bee)
10-24-04 17:44
No 537480
An Overview
roger2003
(Hive Bee)
10-24-04 20:27
No 537495
Psyloxy:
You wrote: "But at least for the dealkylation of vanillin / ethyl vanillin there's methods that work w/o it" - does that mean vanillin can be demethylated with pyridine? I know there is literature stating it can be done, but none of the pyridine dealkylation procedures does it explicitly with vanillin. And I didn't find any practical report of a successful vanillin demethylation using py. here, that's why I ask..
indole_amine
(Hive Addict)
10-24-04 20:44
No 537497
../rhodium /methyle
--psyloxy--
(Newbee)
10-24-04 22:26
No 537509
Can anyone throw any light on these couple of lines found in a catalog blurb for piperidine:
Synthesis reagent: Sodium piperidide , prepared with sodamide and piperidine , cleaves both diaryl and aralkyl ethers ; Chem. Ind. (London) , 80 (1957)
...it's turtles all the way down!
(Über-Führer die Ironie)
10-25-04 02:00
No 537549
I don't get it. Why don't you demethylate vanillin with HI (phosphoric/KI)? it will give high yiled.
(Hive Bee)
10-25-04 05:41
No 537605
..why don't you give "us" any ref's?
indole_amine
(Über-Führer die Ironie)
10-25-04 22:34
No 537766
The Cleavage of Ethers
Robert L. Burwell, , Jr.;
Chem. Rev.; 1954; 54(4); 615-685.
(Hive Addict)
10-26-04 01:49
No 537803
Could the same be done with eugenol?
More than likely you would encounter yields with the alkene taken up by HI but you would get
4-(2-iodopropyl)benzene-1,2-diol (name chem draw gave it)
Right? then the use of the failed iodosafrole routes use methylamine fb to take it back to the alkene and work with it to get safrole?
I dont know.... ive been dreaming so my heads a bit frazzeled...
-AC
Its just my opinion, but no-one listens to me anyway, and rightly so...
(Über-Führer die Ironie)
10-26-04 02:43
No 537810
I'm not sure I fully understand you, but yeah, HI would add across the doublebond and you'll end up with 2-iodo-propyl-whatever as well, i was mostly talking about demethylation of vanillin as I find it pretty amusing that this guy actually requested a ref in Wanted Refs for the synthesis of pyridine in order use it to cleave that damn methyloxy of vanillin.
Right? then the use of the failed iodosafrole routes use methylamine fb to take it back to the alkene and work with it to get safrole?
you'll also cleave the methylenedioxy using HI on safrol..
Again, I don't understand what you meen. The halosafrol route seems to allways bee low-yielding when you do an sn2, i think it might very well give good yields if you switched to sn1. You could use a silver salt to change the course to dominating sn1 when you have a secondary alkyl halide. Maybee an expensive route using silver azide would give high yileds of MDA. Argh, i don't know, MDA compounds are not interesting IMO....
(Hive Addict)
10-26-04 09:57
No 537876
There's a mistake in my translation of the patent in Post 537223 (psyloxy: "preparation of pyridine", Chemistry Discourse) : it should be Fe2(SO4)3 instead of FeSO4.
I mixed up ferri with ferro... maybe a moderator can edit my original posting, I don't want to be a source of 'faulty information from the internet'
--psyloxy--
(Hive Addict)
10-26-04 15:02
No 537906
sorry about my confusion....
what i was saying is that after you cleave the ether with HI you will end up having the diol but also the HI will add across the double bond....
But using an amine freebase on the 2-iodo compound you would (by using sn2) revert it back to the double bond and drop out an amine iodide.
Heres a picture, my explainations always suck ass....
Sound logical? then work with methylation routes to get safrole..... dont know about yields but its definatly easy if it would work....
So im deliberatly using the failure of sn2 mechanism to get the alkene to come back...
-AC
Its just my opinion, but no-one listens to me anyway, and rightly so...
(Hive Bee)
10-26-04 15:28
No 537910
Eugenol can easily be demethylated in one step with pyridine hydrochloride in a domestic microwave oven. Sadly this is not the case with vanillin..
indole_amine
(Hive Addict)
10-27-04 10:59
No 538084
all well and good if one can get hold of (in oz) cat 1 pyridine...
by using this method to make pyridine we need acess to its precursors, 1,5-pentanedial, and thats not to easy as it is not common material, makes them easily traced.
Other than that its easy to get the other materials....
Its just my opinion, but no-one listens to me anyway, and rightly so...
(Moderator)
10-28-04 04:31
No 538233
While hydrogenations of pyridine forming piperidine have been the topic of many Hive posts; the corresponding dehydrogenation of piperidine forming pyridine seems to have escaped notice so far
This reaction can bee carried out either by heating to 300° with concentrated sulphuric acid, or with nitrobenzene at 200°; or with silver acetate in acetic acid An old preparation of piperidine is by heating pentamethylenediamine hydrochloride (cadaverine); which is the result of putrefactive enzymes on lysine; an alternative synthesis can bee found in Ber 56 625-30 (1926):
Cadaverine is quite toxic in addition to being very obnoxious, but the hydrochloride salt isn't so toxic
Chemistry is our Covalent Bond
(Hive Bee)
10-28-04 08:44
No 538272
Maybe catalytic dehydrogenation (Pd/C under vacuum) would also give a nice route from piperidine to pyridine?
indole_amine
(Hive Bee)
10-29-04 02:51
No 538398
(Rated as: excellent)
Influence of Hydrogen Bonding in the Activation of Nucleophiles: PhSH-(Catalytic) KF in N-Methyl-2-pyrrolidone as an Efficient Protocol for Selective Cleavage of Alkyl/Aryl Esters and Aryl Alkyl Ethers under Nonhydrolytic and Neutral Conditions
(Chakraborti, A. K.; Sharma, L.; Nayak, M. K.)
J. Org. Chem., 67 (8), 2541 -2547, 2002
Abstract:
The nucleophilicity of arenethiols can be augmented via hydrogen bonding with 'naked' halide anion. The activity of the halide anions follow the order F- Cl- ~ Br- ~ I- and is dependent on the countercation (Bu4N ~ Cs ~ K > Na Li). The solvent plays an important role in nucleophilic activation as well as regeneration of the effective nucleophile (e.g. ArS-) and those with high dielectric constant, high molecular polarizability, high donor number (DN), and low acceptor number (AN) are the most effective. Selective deprotection of alkyl/aryl esters and aryl alkyl ethers can be achieved under nonhydrolytic and neutral conditions by the treatment with thiophenol in 1-methyl-2-pyrrolidone (NMP) in the presence of a catalytic amount of KF. Aryl esters are selectively deprotected in the presence of alkyl esters and alkyl methyl ethers during intramolecular competitions.
(table 5 looks very interesting; they claim a 79% yield for dealkylating substituted benzaldehydes)
indole_amine