The tautomeric 1,4-dioxygenated pyridazinoindole 1 exists in aqueous solution as a mixture of all four tautomeric forms 1a - 1d, The predominant tautomeric form is the 4-hydroxy-1-oxo compound 1b. The relative abundance of the four forms 1a reversible arrow 1b reversible arrow 1c reversible arrow 1d at equilibrium is 10(4.93):10(8.03):10(3.61):1.
The tautomeric 1,4-dioxygenated pyridazinoindole 1 exists in aqueous solution as a mixture of all four tautomeric forms 1a - 1d, The predominant tautomeric form is the 4-hydroxy-1-oxo compound 1b. The relative abundance of the four forms 1a reversible arrow 1b reversible arrow 1c reversible arrow 1d at equilibrium is 10(4.93):10(8.03):10(3.61):1.