H-1 AND C-13 NMR-STUDIES ON 5,11-DIMETHYL-5H-INDOLO[2,3-B]QUINOLINE AND SOME OF ITS DERIVATIVES

The H-1 and C-13 NMR spectra of the parent 5-methyl-5H-indolo[2,3b-qui noline] and 5,11-dimethyl-5H-indolo[2,3b]quinoline and nine various me thyl, methoxy and fluoro derivatives of the latter have been measured and analysed by the use of COSY, HETCOR, COLOC and selective decouplin g experiments. This gave unambiguous assignment of all signals in the spectra studied; proton-proton coupling constants across three, four a nd five bonds have also been determined. The most interesting result f ound concerns a very large increase in the shielding of carbon 1 upon introduction of a methyl group at C11. This effect is dramatically enh anced by subsequent substitution with a methoxy group at C2.