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Microwave Assisted Quaternisation of an indole; 1,2,3,3-Tetramethyl-3H-indolium iodide

SyntheticPage 841
DOI: 10.1039/SP841
Submitted Jul 10, 2018, published Jul 10, 2018
Robert Smith (, William Stockburn (, Mark Wainwright (, Clare Lawrence (
A contribution from Smith Group

			Reaction Scheme: <IMG src="/images/empty.gif">Microwave Assisted Quaternisation of an indole<IMG src="/images/empty.gif">

Chemicals Used

2,3,3-Trimethylindolenine (Sigma Aldrich)

Iodomethane (Sigma Aldrich)


2,3,3-Trimethylindolenine (0.48 g, 3.00 mmol), iodomethane (0.43 g, 3.00 mmol) and acetonitrile (3 mL) were added to a 35 mL CEM microwave reaction vessel and irradiated at 120oC for 10 minutes. The precipitate formed was isolated at the pump and washed with ethyl acetate (20 mL) and cold diethyl ether (10 mL) and dried in vacuo to give 1,2,3,3-tetramethyl-3H-indolium iodide  (0.76 g, 84%) as a pink solid.

Author's Comments

The authors found the above synthesis to not require purification.  The microwave used for this synthesis was a CEM Discover.  Note the huge signal around 3.33ppm in the 1H & COSY NMR is due to water within the d6-DMSO solvent.


1H NMR (400 MHz, DMSO-d6) δ 7.90 – 7.84 (m, 1H), 7.83 – 7.76 (m, 1H), 7.66 – 7.57 (m, 2H), 3.94 (s, 3H), 2.74 (s, 3H), 1.51 (s, 6H). 13C NMR (101 MHz, DMSO) δ 196.50, 142.50, 142.02, 129.83, 129.31, 123.70, 115.53, 54.39, 35.01, 22.13, 14.39. LCMS m/z: 174.2 [M – I-].

Lead Reference

Angela J. Winstead, Grace Nyambura, Rachael Matthews, Deveine Toney and Stanley Oyaghire. Synthesis of Quaternary Heterocyclic Salts, Molecules 2013, 18, 14306-14319

Other References

Supplementary Information

e.g. Actual NMR spectra (as images or jdx files for interactive spectra), photographs of apparatus, TLC’s or crystals or videos. Please contact the ChemSpider team ( for help with this.
1H NMR (1H NMR.pdf)
13C NMR (13C NMR.pdf)
Mass Spec (MS.pdf)
135-DEPT NMR (135-DEPT NMR.pdf)
135-DEPT vs 13C NMR (135-DEPT vs 13C NMR.pdf)

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Get structure file (.cdx, .sk2, .mol)

Keywords: alkyl/alkenyl/aryl halides, alkylation, amines, heterocyclic compounds, microwave

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