D. Schelz
Nov 1, 1978
Citations
0
Influential Citations
16
Citations
Journal
Helvetica Chimica Acta
Abstract
On the Synthesis of 1-Aryl- and-1-Alkyl-2, 3-dimethyl-quinoxalinium Perchlorates. 2nd Communication1 . Synthesis and 1 H-NMR. Spectra of 2, 3-Dimethyl-1-phenyl-6-X-quinoxlinium Perchlorates The synthesis of the title compounds (5) which have been useful as precursors for a lot of conventional and new-type dyes [2-8] has yet been limited to examples with XH [2] [3] [11] [15] and with electron-donating [4] [12] or at best slightly electron-accepting [1] [6] substituents X and R. We now describe a method suitable even for compounds 5 with strongly electron-accepting substituents: N-monosubstituted o-phenylendiamines 4, were condensed with 2, 3-butanedione and perchloric acid in mixed solvents containing an excess of diethyl ether. The products - mostly substituted at position 6 of the quinoxalinium ring - are chracterized by 1H-NMR. spectra, elemental analyses and in most cases by isolation of the corresponding bases 6. Correlations of chemical shifts with Hammett's σp [18] are given by equations (1)-(5).