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

Selective and efficient alpha-bromination of beta-ketoesters and cyclic and acyclic ketones is achieved by reaction with N-bromosuccinimide (NBS) catalyzed by silica-supported sodium bicarbonate (NaHCO3 center dot SiO2) under mild reaction conditions and with short reaction times. With 100% selectivity with all substrates, after 45 min at room temperature (20 +/- 2 degrees 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 alpha-bromination. The catalysts exhibit activity and reusability.