THE SYNTHESIS AND CHEMISTRY OF AZOLENINES. PART 12. ISOLATION OF INTERMEDIATE 2-HYDROXY-3,4-DIHYDRO-2H-PYRROLES IN THE PAAL-KNORR 1H-PYRROLE SYNTHESIS.

Article abstract of DOI:10.1016/S0040-4020(01)85983-4

Treatment of 1,4-diketones with liquid ammonia gives high yields of isolable 2-hydroxy-3,4-dihydro-2H-pyrrole intermediates.These intermediates, which do not appear to have been observed previously in the Paal-Knorr synthesis with ammonia, have been fully characterized by i.r. and 1H and 13C n.m.r. spectroscopy; in most cases they decompose quantitatively into 1H-pyrroles on standing.The intermediate from hexane-2,4-dione may also be prepared using concentrated aqueous ammonia.