The synthesis of 4-ethyl-2-propyl-3-substitutedpyrrolo[3,4-b]quinoline-1,9- dione derivatives from 3,3-dichloro-4-ethyl-thieno[3,4-b]quinoline-1,9-dione and propylamine

The preparation, spectral properties and structure elucidations of the hitherto undocumented 3-oxo-, 3-thioxo-, 3-propylimino-, 3-imino-, and 3-propylamino- derivatives of 4-ethyl-2-propyl-2,3-dihydro-pyrrolo[3,4-b] quinoline-1,9-dione are described. Mechanistic aspects relating particularly to the formation of the latter two unprecedented products are considered. Magnetic anisotropic effects (deshielding/line broadening of signals) are exhibited by the α-methylene protons of the 4-ethyl moiety in the ¹H NMR spectra of the first four of the above, and in several 3,3-dichloro-thieno[3,4- b]quinoline-1,9-diones and intramolecular H-bonded, 1,2-dialkyl-4-oxo-3- quinolinecarboxylic acid precursor substrates.