Synthesis of Multisubstituted Pyrroles from Enolizable Aldehydes and Primary Amines Promoted by Iodine.

1,2,4-Trisubstituted pyrroles were synthesized from enolizable aliphatic aldehydes and primary aliphatic amines by using iodine as the dual Lewis acid/mild oxidant. In the presence of 3.0 equiv of TBHP, enolizable α,β-unsaturated aldehyde, for example, cocal reacted with aromatic primary amines to form C2-iodized N-arylpyrroles. An acetal-containing pyrrole was successfully prepared from 4-aminobutyraldehyde diethyl acetal, which can be converted easily to 5,6,7,8-tetrahydroindolizine derivatives.