1419209-46-3

Upstream product

• 83-34-1 3-Methylindole 
• 4238-71-5 1-benzylimidazole 

Downstream Products

• 1419209-52-1 2-(1-benzyl-1H-imidazolium-3-yl)-3-methylindolate 
• 1419209-58-7 1-benzyl-3-(3-methyl-1H-indol-2-yl)-1H-imidazole-2(3H)-thione 

Relevant academic research and scientific papers

N-Heterocyclic carbenes from ylides of indolyl-imidazolium, azaindolyl-imidazolium, and indolyl-triazolium salts, and their borane adducts

Indol-2-yl-imidazolium salts were deprotonated at N1 of the indole ring to give ylides. Their tautomeric N-heterocyclic carbenes (NHCs) were trapped by sulfur to give imidazole-2-thiones. Treatment of the ylides with triethylborane resulted in the formation of zwitterionic borane adducts. An analogous sequence of reactions was performed with 8-azaindol-2-yl-imidazolium salts, which served as precursor to prepare first representatives of a new heterocyclic ring system on reaction of their NHC-tautomers with triethylborane. Similarly, an indol-2-yl-1,2,4-triazolium salt was examined with respect to ylide-NHC tautomerism and trapping reactions. A nucleophilic ring transformation of indol-3-amine with a 1,3,4-oxadiazolium salt gave an indol-3-yl-triazolium salt, which was converted into a triazolethione by trapping of the tautomeric N-heterocyclic carbene of its ylide.

Betaine-carbene interconversions. from N-ylides to zwitterionic n-heterocyclic carbene-borane adducts

In the presence of NBS 3-methylindole reacted with various imidazoles to give the (indol-2-yl)imidazolium salts 21a-f, which were converted in aqueous solution into the 2-(imidazolium-3-yl)-3-methylindolates 22a-f by base. These conjugated ylides - which represent a subclass of mesomeric betaines - are the exclusively detectable form in the NMR spectra taken in DMSO-d6. A DFT calculation revealed that the betaine 22a is -9.3 kJ/mol more stable than the tautomeric N-heterocyclic carbene 23a and that the energy for the betaine-carbene interconversion is ΔGa?§§ = 66.4 kJ/mol. The N-heterocyclic carbenes (3-methyl-indol-2-yl)imidazol-2-ylidenes, however, can be trapped by sulfur, triethylborane, and triphenylborane. Whereas the first trapping reaction yielded the expected imidazolethiones, the borates gave the first representatives of new zwitterionic borane adducts, imidazo[2′,1′:3,4][1,4,2]diazaborolo[1,5-a]indolium-11-ides 26a-h. We performed DFT calculations on the structures of mesomeric betaine 22a, the carbene 23a, and the mechanisms of the borane adduct formation to 26a-h, NMR spectroscopic investigations including 15N, 7Li, and 11B NMR spectroscopy, and an X-ray single-crystal analysis of one of the borane adducts.