Simple and Efficient System for the α-Bromination of a β-Ketoester by Using N-Bromosuccinimide in the Presence of Silica-Supported NaHCO₃ as the Heterogeneous Catalyst: An Environmentally Benevolent Approach

Abstract

Selective and efficient α-bromination of β-ketoesters and cyclic and acyclic ketones is achieved by reaction with N-bromosuccinimide (NBS) catalyzed by silica-supported sodium bicarbonate (NaHCO₃ · SiO₂) under mild reaction conditions and with short reaction times. With 100% selectivity with all substrates, after 45 min at room temperature (20 ± 2 °C), conversions for ethylacetoacetate were 67% and for acetophenone, cyclohexanone, and cycloheptanone were 58, 50, and 55%, respectively. Acetyl acetone recorded 65% conversion with 100% selectivity. Although cyclopentanone and toluene had only 20% conversion, both reactions showed 100% selectivity toward α-bromination. The catalysts exhibit activity and reusability.

GRAPHICAL ABSTRACT

Keywords:

• Acyclic ketones
• α-bromination
• β-ketoesters
• NaHCO₃-SiO₂ catalyst
• NBS (N-bromosuccinimide)

Notes

Notes. Ethylacetoacetate, 1.0 mmol; NBS, 1.2 mmol; catalyst, 200 mg. Temperature, 20 ± 2 °C.

^a Mean of duplicate runs.

Notes. Substrate, 1.0 mmol; NBS, 1.2 mmol, and catalyst, 200 mg. Reaction duration, 45 min. Temperature, 20 ± 2 °C.

^a Mean duplicate runs.