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6345090 
Journal Article 
Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr.HCl, IMes.HCl and IXy.HCl 
Hintermann, L 
2007 
Yes 
Beilstein Journal of Organic Chemistry
ISSN: 1860-5397 
3 
22 
English 
17725838 
WOS:000251967500001 
The 1,3-diaryl-imidazolium chlorides IPr.HCl (aryl = 2,6-diisopropylphenyl), IMes.HCl (aryl = 2,4,6-trimethylphenyl) and IXy.HCl (aryl = 2,6-dimethylphenyl), precursors to widely used N-heterocyclic carbene (NHC) ligands and catalysts, were prepared in high yields (81%, 69% and 89%, respectively) by the reaction of 1,4-diaryl-1, 4-diazabutadienes, paraformaldehyde and chlorotrimethylsilane in dilute ethyl acetate solution. A reaction mechanism involving a 1,5-dipolar electrocyclization is proposed.