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Note | Regular issue | Vol 57, No. 12, 2002, pp.2365-2371
Published online, 1st January, 1970
DOI: 10.3987/COM-02-9587
Tautomerism and X-ray Structure of Dihydro-5H-1,3,4-benzotriazepin-5-ones

Jalal A. Zahra, Bassam A. Abu Thaher, Mustafa M. El-Abadelah,* and Martti Klinga

*Chemistry Department, Faculty of Science, University of Jordan, Amman 11942, Jordan


Single X-Ray crystal structure determination of dihydro-5H-1,3,4-benzotriazepin-5-one (2b) revealed that the mobile hydrogen is σ–bonded to N1, while the double bond is situated between C2-N3. In this prevailing 1,4-dihydro tautomer (2A) ( preferred over the alternate 3,4-dihydro form 2B ), both azomethine C2-N3 atoms are folded away, out of the plane comprising the rest bicyclic skeletal atoms, in a “boat”-like manner. Cyclocondensation of the C-acetylcarbohydrazonamides (1a, b) with acetic anhydride is reinvestigated and found to deliver the respective 2a, b, but not the isomeric 4-(3H)quinazolinones (3a, b) as was previously reported.