Imidazole-Catalyzed Henry Reactions in Aqueous Medium

Abstract

2-Nitroalkanols can be efficiently synthesized using imidazole as a mild Lewis basic catalyst in aqueous medium as well as in organic solvents. The products have been found in good yields without purification (> 95% purity by ¹H NMR) for aromatic aldehydes. Additionally, the very mild reaction conditions prevent the particular side reactions such as aldol condensation, Cannizzaro reaction, or dehydration of the 2-nitro alcohols into nitro alkenes even if aromatic aldehydes are used. This report satisfies the criteria for green synthesis in terms of reaction medium and recycling of the catalyst (imidazole).

Keywords:

• Aqueous medium
• Henry reaction
• imidazole
• nitroalkane

ACKNOWLEDGMENT

The authors are thankful to the Council of Scientific and Industrial Research, New Delhi, India, for granting a research grant (No. 01(2067)/06/EMR-II) to R. B.

Notes

^a Reactions were carried out on a 0.5-mmol scale (2 ml of solvent) in the molar ratio of aldehyde/nitromethane/catalyst = 1:3:0.25.

^b Isolated yields of pure products.

^a All products were characterized by FT-IR, ¹H NMR, CHN analyzer and also their comparison with authentic sample.

^b Isolated yields.