Pyrrole studies, Part 48. 1 13 C NMR characterisation of imines and related compounds derived from pyrrole-2-carboxaldehydes and pyrrole-2,5-dicarboxaldehydes

In contrast with the imines formed from monoaminoalkanes and α,ω -diaminoalkanes with pyrrole-3,4-dicarboxaldehydes, which exist in a tautomeric 3H-pyrrole form, pyrrole-2-carboxaldehydes and -2,5-dicarboxaldehydes react with amines to produce 1H-pyrrolyl-methylenimines. Pyrrole-2,5-dicarboxaldehydes with 1,2-diamino-ethane and with 1,3-diaminopropane yield symmetrical macrocyclic systems, contrary to earlier reports.