Iron(III)-Catalyzed Consecutive Aza-Cope−Mannich Cyclization: Synthesis of <i>trans</i>-3,5-Dialkyl Pyrrolidines and 3,5-Dialkyl-2,5-dihydro-1<i>H</i>-pyrroles

Abstract

An efficient alkene aza-Cope-Mannich cyclization between 2-hydroxy homoallyl tosylamine and aldehydes in the presence of iron(III) salts to obtain 3-alkyl-1-tosyl pyrrolidines in good yields is described. The process is based on the consecutive generation of a γ-unsaturated iminium ion, 2-azonia-[3,3]-sigmatropic rearrangement, and further intramolecular Mannich reaction. Iron(III) salts are also shown to be excellent catalysts for the new aza-Cope-Mannich cyclization using 2-hydroxy homopropargyl tosylamine.