RESUMEN
Without the use of catalysts and oxidants, a facile and sustainable electrochemical bromination protocol was developed. By introducing the directing groups, the regioselectivity of pyridine derivatives could be controlled at the meta-position utilizing the inexpensive and safe bromine salts at room temperature. A variety of brominated pyridine derivatives were obtained in 28-95% yields, and the reaction could be readily performed at a gram scale. By combining the installation and removing the directing group, the concept of meta-bromination of pyridines could be verified.
RESUMEN
A facile and sustainable electrochemical umpolung of bromide ion protocol was developed under mild reaction conditions. Transition metal catalysts and exogenous chemical oxidants were obviated for the bromination of Câ»H bond. Notably, graphite rod, which is commercially available at supermarkets and is inexpensive, was employed as the electrode material. This operationally easy and environmentally friendly approach accomplished the synthesis of 3-bromoindole in excellent yield and regioselectivity.