Quinoxalin liquid-phase synthesis

Scheme 7.69 Liquid-phase synthesis of quinoxalin-2-ones.

In a closely related study, Tung and Sun discussed the microwave-assisted liquid-phase synthesis of chiral quinoxalines [80], Various L-a-amino acid methyl ester hydrochlorides were coupled to MeOPEG-bound ortho-fluoronitrobenzene by the aforementioned ipso-fluoro displacement method. Reduction under microwave irradiation resulted in spontaneous synchronous intramolecular cyclization to the corresponding l,2,3,4-tetrahydroquinoxalin-2-ones (Scheme 7.71). Retention of the chiral moiety could not be monitored during the reaction, but after release of the desired products it was found that about 10% of the product had undergone racemization. 

The advantages of MW technology combined with liquid-phase combinatorial chemistry were also successfully applied to a rapid synthesis of quinoxalin-2-ones. PEG bound o-fluoronitrobenzene 716 was synthesized by coupling of 4-fluoro-3-nitrobenzoic acid (715) with PEG 714, in the presence of DCC and a catalytic... 

Attanasi OA, De Crescentini L, Filippone P, Mantellini F, Santeusanio S (2001) A new convenient liquid- and solid-phase synthesis of quinoxalines from (E)-3-diazenylbut-2-enes. Helv Chim Acta 84(8) 2379-2386. doi 10.1002/1522-2675(20010815)... 

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