Regiospecific Photochemical Synthesis of Methylchrysenes |
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Authors: | Thomas Bö hme,Mari Egeland,Marianne Lorentzen,Mohamed F. Mady,Michelle F. Solbakk,Krister S. Sæ bø ,Kå re B. Jø rgensen |
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Affiliation: | 1.Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, P.O. Box 8600, N-4036 Stavanger, Norway;2.Department of Chemistry and Earth Sciences, College of Arts and Sciences, Qatar University, Doha P.O. Box 2713, Qatar |
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Abstract: | Methylated polycyclic aromatic hydrocarbons (PAHs) are suspected to be some of the toxic compounds in crude oil towards marine life and are needed as single compounds for environmental studies. 1-, 3- and 6-methylchrysene (3a,b,c) were prepared as single isomers by photochemical cyclization of the corresponding stilbenoids in the Mallory reaction using stoichiometric amounts of iodine in 82-88% yield. 2-methylchrysene (3d) was prepared by photochemical cyclization where the regioselectivity was controlled by elimination of an ortho-methoxy group under acidic oxygen free conditions in 72% yield. These conditions failed to form 4-methylchrysene from the corresponding stilbenoid. All stilbenoids were made from a common naphthyl Wittig salt and suitably substituted benzaldehydes. We have also demonstrated that methylchrysenes can be oxidized to the corresponding chrysenecarboxylic acids by KMnO4 in modest yields. |
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Keywords: | polycyclic aromatic hydrocarbon, Mallory reaction, oxidative 6π -electrocyclization, eliminative photochemical cyclization, formylation, methylated PAH, PAH metabolite, oxidation |
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