I've tried several methods: HVI/K2CO3 with purification on silica, product decomposed on silica; KMnO4 on alumina, yields were nearly zero; now trying TCCA/DBU at -15, may be working but purification is an issue. If anyone has successfully employed these or other methods, please let me know! References for above methods:
JACS 2016 138 (25) 7820
Bioorg. & Med. Chem Let 2004 14 6079
Syn. Lett. 2004 15 2803 (procedure is in SI)
Mr. Wozniak,
The employment of KMnO4 has been regarded as a recommendable approach. Have you any optimization of the reaction conditions?
Both of these claim 90%+ yields, but I couldn't find them unlocked so you will have to request them.
Article Alumina Supported Potassium Permanganate: An Efficient Reage...
Article Novel, Mild and Chemoselective Dehydrogenation of 2-Imidazol...
These are two of the references I listed above. The KMnO4/Al2O3 claims 90% yields, I've gotten basically 0% trying it. The TCCA method works but the purification is terrible and the article offers no help
Oh sh*t sorry, adhd.
The first paper contains a number of methods with their respective sources, the second one is not very specific but I'm sure there's a more specific guideline out there using Rinney Nickel.
https://core.ac.uk/download/pdf/14736679.pdf
http://www.chemicalbook.com/ChemicalProductProperty_EN_CB6146227.htm
The purification issue I've been having has been separating the product from the remaining imidazoline after reaction, that first reference claims tol/hex works for recrystallizing it. I'll give that a shot, I've been beating my head against a wall watching everything streak on tlc and columns (even on alumina) so that would certainly make my life much easier! Thanks!
For some reason I can't open these pdfs anymore, they're giving me an error that the site is no longer available? If possible, could you email me the actual pdf files please? my email is [email protected] . Thanks!
I may have used some university credential, I downloaded the PDF now, so you should be able to see it.
The other one has just a paragraph that's relevant so I'll copy-paste
Production
1. The product is produced by the following steps: glyoxal, acetaldehyde and ammonia are used as raw materials to produce crude products of 2-methylimidazole after reaction, and then refined by sublimation.
2. Use ethylenediamine and acetonitrile as raw materials, and them react in the presence of sulfur to generate imidazoline., The dehydrogenation occurs below 20℃ with nickel as catalyst to get 2-methylimidazole products.
3. Products can be obtained by reaction of glyoxal and methylamine in the presence of formaldehyde.
4.It can be obtained by dehydrogenation of 2-methylimidazole. Heat 2-methylimidazoline to molten (melting point of 107℃), add active nickel carefully, heat up to 200-210℃ and react for 2h. Cool to 150℃, then add water for dissolving, filter press while hot, separate active nickel, concentrate the filtrate to the temperature at 140℃, discharge and cool to get 2-methylimidazole. The purity of products produced with this method is more than 98%. Product consumes (95%) 1095kg ethylenediamine and 975kg acetonitrile. Using glyoxal and aldehyde as raw materials is better.
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