1,4-二羰基化合物合成吡咯和喹喔啉的研究

Pyrrole is an important heterocyclic compound that not only appears in molecular frameworks with biological and pharmacological activities but is also used in the preparation of conductive functional materials for electroluminescent devices.Among the various synthetic strategies, the Paal-Knorr reaction, using Br⌀nsted acids or Lewis acids to catalyze the reaction between primary amines and 1,4-dicarbonyl precursors, is regarded as one of the most attractive and efficient approach for constructing pyrrole frameworks.To access structurally novel pyrrole-fused ring systems, diverse synthetic routes toward polysubstituted pyrroles has been developed based on the methodologies used for indole construction.This study investigates the reaction of pyrrolylaniline with dicarbonyl compounds under acidic conditions to construct novel pyrrole and pyrrole-fused derivatives, thereby expanding the efficient synthesis of nitrogen-containing heterocyclic derivatives.Using ortho-pyrrolylaniline and 1,4-dicarbonyl compounds(2,5-hexanedione) or 1,4-ketoesters as starting materials, the reactions were carried out in the presence of p-toluenesulfonic acid monohydrate.Optimization of the reaction conditions, including solvent, reaction temperature, and catalyst loading, afforded pyrrole and pyrrole-fused ring compounds in moderate yields.All products were characterized by ~1HNMR,13CNMR,and HRMS,while the relative configurations of the new compounds were determined by single-crystal X-ray diffraction.Based on control experiments, a plausible reaction mechanism was proposed, and the reaction intermediates were confirmed by two-dimensional NMR spectroscopy.This work established a p-toluenesulfonic acid monohydrate-catalyzed tandem reaction between ortho-pyrrolylaniline and 1,4-dicarbonyl compounds, delivering target products with high chemoselectivity and regioselectivity.The influence of the structure of the dicarbonyl compounds on product selectivity was also elucidated, providing a new strategy for the synthesis of nitrogen-containing heterocyclic compounds.