- A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates
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Easily obtainable cyclic enaminones (piperidin-2-ylidenealkanones) can be transformed into substituted bicyclic pyridazinium tetrafluoroborates upon treatment with corresponding diazonium salts. The transformation can be performed either in a one-pot way or in a two-step process with the isolation of single azo-coupled enaminone as the intermediate. The former method is superior. Under the optimized conditions, a number of pyridazinium salts substituted with both electron-donating and electron-withdrawing substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by using a more reactive diazonium salt before a less reactive one.
- Josefik, Frantisek,Svobodova, Marketa,Bertolasi, Valerio,Simunek, Petr
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supporting information
p. 1463 - 1471
(2013/08/23)
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- Stilbene and Azobenzene Diazonium Compounds as Dye Reagents for Crown Ethers
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The change of light absorption of six coloured diazonium compounds (1, 2a, 2b, 3, 4, 5) on complexation with five 18-crown-6 derivatives (6-10) in 1,2-dichloroethane was investigated.In the benzene, stilbene and azobenzene series complexation produces only hypsochromic shifts of the intramolecular ct-band of the diazonium ions up to 140 nm.The extend of the shift is effected by ion pairing.The ct-transition energy of the complexes diazonium ion is independent on the present anion in contrast to the uncomplexed compounds.The colour changes are not caused by host to guest charge transfer or E/Z-isomerisation of the stilbene and azobenzene derivatives.A quantitative explanation of the colour changes is given basing on an electrostatic interaction model.
- Walkow, F.,Israel, G.
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p. 835 - 840
(2007/10/02)
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- Photochemistry of Adsorbed Molecules. V. E.S.R.-Investigations of Phenyl Cations during Photolysis of Arendiazonium Salts in the Polycrystalline and the Adsorbed State
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During photolysis of 4-NR2-substituted arene diazonium salts ground state triplets occur at low temperatures in the e.s.r.-spectra with (?)5(sp2)1 configuration in the polycrystalline as well as in the adsorbed state on SiO2.The influence of anions and the reaction order of decay processes are discussed.The decay of the aryl cations were also investigated in the presence of pyrene as ?-electron donor.Reaction takes place with coadsorbed molecules and the decay mechanism changes from ionic character to radical character.
- Baezold, D.,Fassler, D.,Kunert, R.
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p. 209 - 216
(2007/10/02)
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