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Photochemistry of 1,4-Dihydropyridine Derivatives: Diradical Formation, Delocalization and Trapping as a Route to Novel Tricyclic and Tetracyclic Nitrogen Heterocyclic Ring Systems

Department of Chemistry, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait
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Academic Editors: Scott Reed and Marino Resendiz
Molecules 2016, 21(7), 866; https://doi.org/10.3390/molecules21070866
Received: 2 June 2016 / Revised: 22 June 2016 / Accepted: 25 June 2016 / Published: 30 June 2016
(This article belongs to the Special Issue Photoactive Molecules)
Irradiation of an acetonitrile solution of 4-aryl-3,5-dibenzoyl-1,4-dihydropyridine derivatives 1ac and maleimides 2ac using medium pressure Hg-arc lamp (λ > 290) nm afforded three different cycloadducts 4, 5, 6 in addition to the oxidation products 3. These results indicate that compounds 1ac undergoes intermolecular cycloaddition reaction through three biradical intermediates and behave photochemically different than those reported previously for the analogous 3,5-diacetyl and 3,5-dicarboxylic acid derivatives. The present work also offers simple access to novel tricyclic and tetracyclic nitrogen heterocyclic ring systems of potential biological and synthetic applications. The structure of the photoproducts was established spectroscopically and by single crystal X-ray crystallography. View Full-Text
Keywords: photochemistry; 1,4-dihydropyridines; dihydropyrrolo[3’,4’4,5]cyclopenta[1,2-b]-pyridine; 4,11-diazatetracyclo[5,3,1,02,6,08,10]undecane; tetrahydropyrrolo[3’,4’:5,6]pyrano[4,3-b]-pyridine photochemistry; 1,4-dihydropyridines; dihydropyrrolo[3’,4’4,5]cyclopenta[1,2-b]-pyridine; 4,11-diazatetracyclo[5,3,1,02,6,08,10]undecane; tetrahydropyrrolo[3’,4’:5,6]pyrano[4,3-b]-pyridine
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MDPI and ACS Style

Al-Jalal, N.A.; Ibrahim, Y.A.; Al-Awadi, N.A.; Ibrahim, M.R.; Sayed, O.M. Photochemistry of 1,4-Dihydropyridine Derivatives: Diradical Formation, Delocalization and Trapping as a Route to Novel Tricyclic and Tetracyclic Nitrogen Heterocyclic Ring Systems. Molecules 2016, 21, 866.

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