4.

Synthesis of benzimidazol-2-thiones from dimedone : An unexpected cyclisation into a five-membered ring

Norah Bennamane, Karima Zaïoua, Yamina Akacem, Rachedine Kaoua, Yamina Bentarzi, Saliha Bakhta, Bellara Nedjar-Kolli and Lahcen Ouhab

Org. Commun. (2009), 2:2 ; 49-59<

Laboratory of applied organic chemistry, University of Sciences and Technology  Houari Boumediene, BP 32, El-Alia, Algiers, Algeria.

Laboratoiry of thermodynamic and modelisation, USTHB, Algeria .

UMR 6226 CNRS-UR, Sciences chimiques de Rennes, Organométalliques et matériaux Moléculaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex France.

Abstract: When enaminones 9 obtained from dimedone were used instead of furanone 3 and pyranone 4 in the reaction with carbon disulfide in presence of pyridine, a crystalline product was formed whose spectral data and X-Ray structure were inconsistent with the benzodiazepine-thiones 5-6 but agreed with the structure of benzodimidazol-2-thione 11 which is expected to possess a notable pharmacological activities. Theoretical calculations, with DFT/B3LYP method, have been carried out to rationalize the experimental results.

Keywords: Dimedone; enaminones; benzimidazol-thiones; benzodiazepines; carbon disulfide.