Journal fur Praktische Chemie - Chemiker-Zeitung p. 262 - 268 (1993)
Update date:2022-08-11
Topics:
Gruenefeld, J.
The pyridinium ring of squaric acid betaines (2) is opened by hydroxide ions.Electronegative substituents (R = Cl, CN) at C-3 promote this reaction.The stereochemistry of the resulting 5-(2-hydroxy-3,4-dioxocyclobut-1-en-1-yl)aminopenta-2,4-dienales (3) is confirmed by NMR-spectroscopy.Treatment of 3 with sodium hydroxide results in further hydrolysis to the sodium salts of glutaconaldehydes (5) and 3-amino-4-hydroxycyclobut-3-ene-1,2-dione (6).These products are also directly obtained from the nicotinic acid derivates 2d (R = COOEt) and 2e (R = CONH2), in the latter case cyclisation of the glutaconic acid derivate to the known 3-formylpyrid-2-one (10) is observed.
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