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Molecules 2013, 18(11), 14293-14305; doi:10.3390/molecules181114293

The Formation of 2,2,4-Trimethyl-2,3-dihydro-1H-1,5-Benzodiazepine from 1,2-Diaminobenzene in the Presence of Acetone

1 Department of Chemistry, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031, South Africa 2 Department of Chemistry, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa
* Author to whom correspondence should be addressed.
Received: 11 September 2013 / Revised: 11 November 2013 / Accepted: 11 November 2013 / Published: 19 November 2013
(This article belongs to the Section Organic Synthesis)
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In an attempt to synthesize a 2-substituted benzimidazole from the reaction of o-phenylenediamine and isophthalic acid in the presence of acetone and ethanol under microwave irradiation, a salt of the isophthalate ion and 2,2,4-trimethyl-2,3-dihydro-1H-1,5-benzodiazepin-5-ium ion was obtained. The condensation of two moles of acetone with the amine groups resulted in the formation of the benzodiazepine which crystallized as an iminium cation forming a salt with the isophthalate anion. The formation of benzodiazepine was also confirmed by performing the reaction of o-phenylenediamine with excess acetone in ethanol under conventional heating conditions. The compounds were characterized by NMR, FTIR, HRMS and microanalysis as well as X-ray crystallography. The reaction mechanism leading to the formation of benzodiazepine is also discussed.
Keywords: o-phenylenediamine; acetone; benzodiazepine o-phenylenediamine; acetone; benzodiazepine
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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Odame, F.; Kleyi, P.; Hosten, E.; Betz, R.; Lobb, K.; Tshentu, Z. The Formation of 2,2,4-Trimethyl-2,3-dihydro-1H-1,5-Benzodiazepine from 1,2-Diaminobenzene in the Presence of Acetone. Molecules 2013, 18, 14293-14305.

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