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Note | Regular issue | Vol 60, No. 4, 2003, pp.925-932
Published online, 4th February, 2003
DOI: 10.3987/COM-02-9666
Pyrido[3,4-b]pyrazines. A New Application of 2-Chloro-3,4-diaminopyridine

Werner W. K. R. Mederski,* Dieter Kux, Markus Knoth, and Markus J. Schwarzkopf-Hofmann

*Merck KGaA, Preclinical Pharmaceutical Research, Frankfurter Str. 250, 64271 Darmstadt, Germany


5-Chloropyrido[3,4-b]pyrazines were prepared from 1,2-dicarbonyl compounds and 2-chloro-3,4-diaminopyridine. Condensation of unsymmetrical glyoxals provided a mixture of two regiosiomers with 2-substituted pyrido[3,4-b]pyrazines as the major product. The regiochemistry was unambiguously assigned by 2D-NMR experiments. C-C- and C-N coupling reactions of 5-chloro or 5-oxo intermediates afforded the corresponding C-5 or N-6 substituted derivatives.