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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 (CC BY 3.0).

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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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