Paal–Knorr Pyrrole Synthesis in Water

Abstract

Water was a suitable medium for Paal–Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented.

GRAPHICAL ABSTRACT

Keywords:

• Green chemistry
• hexa-2,5-dione
• Paal–Knorr
• pyrrole
• water

Notes

Note: Reaction conditions: amine (10 mmol), 2,5-hexadione (10 mmol), 5 mL water, 15 min, 100 °C.

^a Amine (5 mmol), 2,5-hexadione (10 mmol), 5 mL water, 15 min, 100 °C.

^b Amine (3.3 mmol), 2,5-hexadione (10 mmol), 5 mL water, 15 min, 100 °C.

n.o., not observed.

Note: Reaction conditions: Aniline (10 mmol), 2,5-hexzadione (10mmol), solvent (5mL), 15min.

Note: Reaction conditions: Benzylamine (10mmol), 2,5-hexzadione (10mmol), solvent (5mL), 15min.