Saccharin as an Organocatalyst for Quinoxalines and Pyrido[2,3-b]pyrazines Syntheses

Abstract

A room-temperature procedure using saccharin as catalyst has been described for the cyclocondensation of different 1,2-arylenediamines with various 1,2-dicarbonyl compounds, yielding either quinoxalines or pyrido[2,3-b]pyrazines. The reactions proceed in very short reaction times in methanol, and the target heterocycles are isolated in quantitative yields after addition of water, filtration, and drying. Substituted pyrido[2,3-b]pyrazines can also be reached regioselectively by reacting α-ketoaldehydes with 2,3-diaminopyridine.

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GRAPHICAL ABSTRACT

Keywords:

• Pyrido[2,3-b]pyrazine
• quinoxaline
• room-temperature reaction
• saccharin

Notes

^a Isolated yield.

^a Isolated yield.

^a Isolated yield.

^b Regioisomers isolated by chromatography over silica gel (eluent: 80/20 CH₂Cl₂–AcOEt).