| Popis: |
The reaction of squaric acid ( 1 ) with phenylhydrazine yields cyclobutanetetraone poly(phenylhydrazones) ( 2–4 ), as reported earlier, as well as squaric acid derivatives, reported here. The latter products are a salt, 1,3-dianilinocyclobutenediylium-2,4-diolate ( 5 ), and 1-anilino-2-phenylhydrazinocyclobutene-3,4-dione ( 6 ), which upon oxidation yields tautomeric forms of cyclobutanetetraone 1-anilide-2-phenylhydrazone ( 7a and 7b ). The structure of the compounds isolated was established by 1 H, 13 C, 2D COSY, and 2D J -resolved NMR spectroscopy. The similarity between the reaction of squaric acid ( 1 ) with phenylhydrazine and osazone formation can be seen from the analogy between compounds 2 , 6 , and 7b and intermediates produced during carbohydrate osazone formation, as well as from the fact that these compounds afford an osazone analog ( 4 ) when treated with phenylhydrazine. It was also found that compound 5 can be generated by a retro-osazone reaction when cyclobutanetetraone bis(phenylhydrazone) ( 2 ) is heated with aniline. |
