Synthese von Glutaconaldehyden aus Quadrats�ure-Pyridiniumbetainen
作者:J. Gr�nefeld
DOI:10.1002/prac.19933350308
日期:——
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.