Multinuclear NMR study of protonation in some indolizine systems

Abstract 1H, 13C and 15N NMR data are presented for seven indolizine derivatives in solutions of dimethyl sulphoxide and trifluoroacetic acid (TFA). The TFA solutions contain species protonated at position N‐1 in all cases. The most definitive evidence for the site of protonation is provided by the 15N results.