
%0 Journal Article
%A Jones, AJ 
%A Hanisch, P 
%A Heffernan, ML 
%A Irvine, GM 
%T <sup>13</sup>C and some <sup>15</sup>N N.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms
%J Australian Journal of Chemistry
%D 1980/03/01
%V 33
%N 3
%P 499-508
%K 
%R https://doi.org/10.1071/CH9800499
%U https://www.publish.csiro.au/paper/CH9800499 
%X The carbon-13 and (in part) nitrogen-15 chemical shifts of 1,2,3- triazaindolizine and seven three ringed analogues of indolizine have been analysed and enable deductions to be made concerning the extent that the free pair of electrons on the bridgehead nitrogen atom contributes to the delocalized electronic structures. Analogies between these molecules and indolizine are noted in that all the systems possess a high degree of aromaticity. Additivity relationships for nitrogen and methyl substitution are compared with those previously reported for other heteroaromatic molecules.    Comparison of previously published 100-MHz and the present-work 270-MHz proton n.m.r. results enabled 13C spectral assignments to be confirmed by selective 1H irradiation experiments, since coupling constant analyses did not provide unambiguous assignments in all cases. One-, two-, three- and four-bond 13C-1H coupling constants are reported for most carbon atoms where first-order spectral analysis was possible. Several examples of non-first-order behaviour are presented and attempts to reconcile the occurrence of this behaviour are outlined. 
