Skeletal Diversity in Catalytic Synthesis of (1,3-Oxazacycloalk-3-ylmethyl)-Substituted Pyrroles

Abstract

A series of bi- and trinuclear pyrrole derivatives was prepared by the 5 mol % ZrOCl₂ ·8H₂O-catalyzed CH-sp²-aminomethylation reaction of pyrrole with bis(1,3-oxazacycloalk-3-yl)methanes. The reaction proceeds at the positions 2, 5 or 2 of pyrrole depending on the amount of aminomethylating reagents obtained from formaldehyde and α,ω-amino alcohols (2-aminoethan-1-ol, 3-aminopropan-1-ol, 4-aminobutan-1-ol). The aminomethylation reaction of indole with bis(1,3-oxazolidin-3-yl)methane proceeds at the position 3. In the case of carbazole, N-aminomethylation proceeds under these conditions.