Indolizine studies. Part 3. Synthesis and dynamic NMR analysis of indolizine-2-carboxamides
Reaction of indolizine-2-carboxylic acids with primary and secondary amines in the presence of 1,1′-carbonyldiimidazole provides convenient and efficient access to the corresponding secondary and tertiary amides and offers a significant improvement on previously reported methodology. The N–CO rotational barriers in the symmetrically substituted tertiary amides have also been explored using variable-temperature 1H and 13C NMR spectroscopy.