Potentially tautomeric pyridazino [4,5-b] indolones

Abstract

This thesis is in five chapters. Chapter I reviews the tautome- rismi classification of tautomerism, heteroaromatic tautomerism and the methods available for the investigations of heteroaromatic tau- tomerism. Chapter II describes the synthesis of the 3,4-dihydro-4-oxo-5H- pyridazino [4,5-b]indoles. Their tautomerism have been studied quali- tatively by comparison of the electronic spectra of the tautomeric system with those of 'fixed structure model' compounds. Measurements of the basicities of the model compounds provided a quantitative evaluation of the tautomeric equilibrium constant (KT). Chapter III, the preparation of 1, 2-dihydro-1-oxo-5H-pyridazino [4,5-b]indoles, and the synthesis of the corresponding 'fixed struc- ture model' compounds for the tautomerism studies are described. The tautomeric behaviour (oxo-hydroxy) of the 1, 2-dihydro-1-oxo-5H- pyridazino[4,5-b]indoles was investigated, qualitatively and quanti- tatively by a comporison of IR, UV, and NMR spectral data and by the determination of the pKa values of the 'fixed structure model' compo- unds. In chapter IV, the preparation of 1, 4-dioxo-1,2,3,4-tetrahydro- 5H-pyridazino [4,5-b]indoles, and the synthesis of the corresponding 'fixed structure model' compounds for the tautomerism studies are described. The tautomeric behaviour (oxo-oxo, oxo-hydroxy, hydroxy- hydroxy) of the 1,4-dioxo-1,2,3,4-tetrahydro-5H-pyridazino[4,5-b] indoles was investigated, qualitatively and quantitatively by a com- parison of IR, UV, and NMR spectral data and the determination of the pKa values of 'fixed structure model' compounds. In chapter V, the synthesis of 4-chloro-, 1-chloro-, and 1, 4- dichloro-5H -pyridazino[4,5-b]indoles from the corresponding 5H-pyri- dazino[4,5-b]indoles is described, together with a study of nucleop- hilic displacement reactions of these compounds with nucleophiles.