A Convenient Synthesis and Spectroscopic Characterization of N,N'-Bis(2-propenyl)-2,7-diazapyrenium Quaternary Salts
N,N'-Bis(2-propenyl)-2,7-diazapyrenium salts are synthesized in good yield from the reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride with allylamine, followed by LiAlH4 reduction and subsequent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The nature of the counteranion depends on the solvent system used for recrystallization of the crude product from the final DDQ-oxidation step. X-ray analysis shows that if recrystallization is carried out in boiling CH3OH/H2O (1:1, v/v), the counteranion in the resulting deep-red crystals is always the alkoxy anion of 2-cyano-5,6-dichloro-3-hydroxy-1,4-benzoquinone, whether the final DDQ oxidation ends with addition of HClO4 or HCl; on the other hand, if recrystallization is carried out with anhydrous acetonitrile, the product is N,N'-bis(2-propenyl)-2,7-diazapyrenium diperchlorate or dichloride depending on whether the DDQ oxidation is followed by addition of concd HClO4 or concd HCl, respectively. Importantly, if the DDQ oxidation is quenched with HBr, Br- is oxidized to Br2 by unreacted DDQ, and the resulting product is N,N'-bis(2,3-dibromopropyl)-2,7-diazapyrenium dibromide. Comparative absorption and time-resolved emission studies provide evidence for possible dimerization of N,N'-bis(2-propenyl)-2,7-diazapyrenium diperchlorate in CH3CN.
L. Sotiriou-Leventis et al., "A Convenient Synthesis and Spectroscopic Characterization of N,N'-Bis(2-propenyl)-2,7-diazapyrenium Quaternary Salts," Journal of Organic Chemistry, American Chemical Society (ACS), Jan 2000.
The definitive version is available at https://doi.org/10.1021/jo0004557
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