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A green, simple, and fast procedure has been developed for the preparation of quinoxaline derivatives by a condensation of 1,2-diamines with 1,2-dicarbonyl compounds in the presence of zirconium oxide modified with tungstophosphoric acid (H 3 PW 12 O 40 ) as a heterogeneous catalyst, in a solvent-free medium using conventional heating. Quinoxaline derivatives were formed in short-time periods and excellent yields (65-100%). The reaction work-up is very simple and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions without appreciable loss of the catalytic activity. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text.

H 3−X PW 12 O 40 ] (3−X)− species interacting electrostatically with the ≡Si-OH 2 + groups, and by potentiometric titration the solids presented very strong acid sites. In summary, they are good candidates to be used in reactions catalyzed by acids, especially to obtain quinoxaline derivatives.

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