Patent DE944251 (http://l2.espacenet.com/dips/viewer?PN=DE944251&CY=gb&LG=en&DB=EPD)
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/carbonsaeuren/darstellungpyridin.htm (http://www.korbis-labor.de/experimente/carbonsaeuren/darstellungpyridin.htm)
.
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 (https://www.thevespiary.org/talk/index.php?topic=11807.msg29191200#msg29191200)
(Antoncho: "Demethylation of vanillin.", Novel Discourse)
Post 351285 (https://www.thevespiary.org/talk/index.php?topic=11807.msg35128500#msg35128500)
(6079_Smith_W_II: "JP10265428", Novel Discourse)
--psyloxy--
https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html#pyralcl3 (https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html#pyralcl3)
--psyloxy--
The Cleavage of Ethers
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_imgs/pdf.gif)
Robert L. Burwell, , Jr.;
Chem. Rev.; 1954; 54(4); 615-685.
There's a mistake in my translation of the patent in Post 537223 (https://www.thevespiary.org/talk/index.php?topic=7098.msg53722300#msg53722300)
(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--
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 ;D 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):
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_imgs/djvu.gif)
Cadaverine is quite toxic in addition to being very obnoxious, but the hydrochloride salt isn't so toxic ;)
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
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_imgs/pdf.gif)
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