P.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms. III. Pyrrolo[2,1-c][1,2,4]benzotriazine

The detailed assignment and analysis of the p.m.r. spectra of solutions of pyrrolo[2,1-c][1,2,4]benzotriazine in dimethyl sulphoxide at 80� and 100�, and in acetic acid at 60�, was carried out. The presence and approximate magnitudes of several inter-ring long-range coupling constants were deduced by comparison of the experimental and theoretically calculated spectra. Spin-tickling experiments were used to determine the relative sign combinations of the intra-ring coupling constants of the protons 1-3 and 6-9 in the particularly favourable case of the acetic acid solution of pyrrolo[2,1-c][1,2,4]benzotriazine. All coupling constants were found to have the same sign, presumably positive.