Search our Database of Scientific Publications and Authors

I’m looking for a

    Details and Download Full Text PDF:
    Mechanistic investigations into the photochemistry of 4-allyl-tetrazolones in solution: a new approach to the synthesis of 3,4-dihydro-pyrimidinones.

    J Org Chem 2006 Apr;71(9):3583-91
    CCMAR, Universidade do Algarve, Campus de Gambelas, 8005-039 Faro, Portugal.
    Photolysis (lambda = 254 nm) of 4-allyl-tetrazolones 2a-c was carried out in methanol, 1-propanol, 1-hexanol, acetonitrile, and cyclohexane. The sole primary photochemical process identified was molecular nitrogen elimination, with formation of pyrimidinones 6a-c. Following the primary photocleavage, secondary reactions were observed in acetonitrile and cyclohexane, leading to phenyl-isocyanate (7), aniline (9), and 1-phenylprop-1-enyl-isocyanate (10a). In alcoholic solutions, the primary products, 6a-c, remained photostable even under extended irradiation, making possible the isolation of 3,4-dihydro-pyrimidinones as stable compounds in very high yields. The observed photostability of pyrimidinones 6a-c in alcohols is ascribed to the excited state quenching via reversible proton transfer, facilitated by the solvent cage stabilization due to formation of hydrogen bonds. The viscosity of alcohols is directly related to the cage effects observed. The photocleavage of 4-allyl-tetrazolones leads probably to a caged triplet radical pair. This hypothesis is confirmed by the solvent viscosity effect on the photolysis quantum yields. Additionally, dissolved molecular oxygen sensitizes the formation of pyrimidinones, as should be expected for a triplet intermediate that can only form the product molecule after T-S conversion, which is accelerated by oxygen.
    PDF Download - Full Text Link
    ( Please be advised that this article is hosted on an external website not affiliated with
    Source Status ListingPossible

    Similar Publications

    Photochemistry of 5-allyloxy-tetrazoles: steady-state and laser flash photolysis study.
    Org Biomol Chem 2008 Mar 14;6(6):1046-55. Epub 2008 Feb 14.
    Department of Chemistry, Biochemistry and Pharmacy, F.C.T. and CCMAR, University of Algarve, 8005-039 Faro, Portugal.
    The photochemistry of three 5-allyloxy-tetrazoles, in methanol, acetonitrile and cyclohexane was studied by product analysis and laser flash photolysis. The exclusive primary photochemical process identified was molecular nitrogen elimination, with formation of 1,3-oxazines. These compounds were isolated in reasonable yields by column chromatography on silica gel and were fully characterized. Read More
    Photochemistry of 1-allyl-4-aryltetrazolones in solution; structural effects on photoproduct selectivity.
    Photochem Photobiol Sci 2013 Feb 14;12(2):272-83. Epub 2012 Sep 14.
    CCMAR and Department of Chemistry and Pharmacy, F.C.T., University of Algarve, P-8005-039 Faro, Portugal.
    The photochemistry of tetrazolones derived from the carbocyclic allylic alcohols cyclohex-2-enol and 3-methylcyclohex-2-enol and from the natural terpene alcohol nerol was investigated in solution with the aim of assessing the effect of solvent and of structural constraints imposed by bulky allylic moieties on photoproduct selectivity and stability. Photolysis of tetrazolones derived from nerol and cyclohex-2-enol afforded the corresponding pyrimidinones as major products through a pathway that appears to be similar to that proposed for other 1-allyl-4-phenyl-1,4-dihydro-5H-tetrazol-5-ones derived from acyclic and unhindered allylic alcohols previously investigated but photolysis of the tetrazolone derived from the bulkier 3-methylcyclohex-2-enol 4c leads to formation of a benzimidazolone, indicating that, in this case, cyclization of the biradical formed upon extrusion of N(2) involves the phenyl substituent and not the allylic moiety. Theoretical calculations (DFT(B3LYP)/3-21G*) were conducted to support the interpretation of the experimental results and mechanistic proposals. Read More
    Photoreduction of Azoalkanes by Direct Hydrogen Abstraction from 1,4-Cyclohexadiene, Alcohols, Stannanes, and Silanes.
    J Org Chem 1997 Nov;62(23):8082-8090
    Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany, the Institut für Physikalische Chemie, Universität Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada.
    A mechanistic investigation of the photoreduction of the n,pi triplet-excited azo chromophore has been carried out on azoalkanes 1, which exhibit efficient intersystem-crossing quantum yields (ca. 0.5). Read More
    The long-lived triplet excited state of an elongated ketoprofen derivative and its interactions with amino acids and nucleosides.
    J Phys Chem B 2007 Jul 23;111(28):8277-82. Epub 2007 Jun 23.
    Instituto de Tecnología Química UPV-CSIC and Departamento de Química, Universidad Politécnica de Valencia, Avda de Los Naranjos s/n, 46022 Valencia, Spain.
    The aim of the present work was to find a ketoprofen (KP) equivalent suitable for time-resolved studies on the interactions of its KP-like triplet state with biomolecules or their simple building blocks, under physiologically relevant conditions. Such a compound should fulfill the following requirements: (i) it should be soluble in aqueous media; (ii) its triplet lifetime should be longer than that of KP, ideally in the microsecond range; and (iii) its photodecarboxylation should be slow enough to avoid interference in the time-resolved studies associated with formation of photoproducts. Here, the glycine derivative of ketoprofen (KPGly) has been found to fulfill all the above requirements. Read More