Silica Sulfuric Acid (SSA)/Polyethylene Glycol (PEG) as a Recyclable System for the Synthesis of Quinoxalines and Pyrazines

Abstract

An efficient and facile method has been developed for the condensation of 1,2-diamines with α-hydroxyketones in polyethylene glycol (PEG) to quinoxalines and pyrazines with good yields in the presence of silica sulfuric acid (SSA). The important features of the methodology are simple operations, environmentally friendliness, and no requirement for metal catalysts. Additionally, the catalyst system (SSA/PEG) could be recovered easily and reused.

Keywords:

• Pyrazines
• quinoxalines
• recyclable catalyst
• silica sulfuric acid

ACKNOWLEDGMENTS

We are grateful to the National Key Technology Research and Development Program (No. 2007BAI34B00), the Natural Science Foundation of Zhengjiang Province (No. Y4080107), and the Technology Innovation Foundation of Zhejiang Province (No. 2010R424014) for financial support.

Notes

^a All the reactions were performed using benzoin 1a (0.5 mmol), 1,2-diaminobenzene 2a (1.0 mmol), and 300 mg of SSA for 2 h.

^b Isolated yield.

^c NR, no reaction.

^d 100 mg of catalyst.

^e 200 mg of catalyst.

^f 400 mg of catalyst.

^a All the reactions were performed using α-hydroxyketone 1 (0.5 mmol), aromatic 1,2-diamine 2 (1.0 mmol), and 300 mg of SSA in PEG-400 (5 mL) at 120 °C for 2 h.

^b Isolated yield.

^c The reaction was carried out for 6 h.

^a All the reactions were performed using α-hydroxyketone 1 (0.5 mmol), aliphatic 1,2-diamine (1.0 mmol), and 300 mg of SSA in PEG-400 (5 mL) at 120 °C for 6 h.

^b Isolated yield.