- Cyclizations. Part 1. Electrochemical and Photochemical Reactions of 1-(4-Fluorophenyl)-5-(2-halogenophenyl)tetrazoles
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Electrochemical reduction of the title compounds, where the halogen substituent is Cl, Br or I, leads to cleavage of the carbon-halogen bond to leave a phenyl radical.Competition then follows between intramolecular radical substitution giving 7-fluorotetrazolophenanthridine and further reduction of the radical, then protonation, giving 1-(4-fluorophenyl)-5-phenyltetrazole.Substitution predominates but reduction and protonation becomes a more competing reaction when the halogen is Br or I.Photochemical reaction of the title compounds shows competition between carbon-halogen bond cleavage to give 7-fluorotetrazolophenanthridine and loss of nitrogen followed by cyclization to give 2-halogenophenyl-5-fluorobenzimidazole.Carbon-halogen bond cleavage predominates and becomes the only reaction when the halogen is I.The fluorine substituent allows the determination of product yields by 19F NMR spectroscopy.
- Donnelly, Shileen,Grimshaw, James,Trocha-Grimshaw, Jadwiga
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p. 1557 - 1562
(2007/10/02)
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