Abstract

Radical halogenation is a fundamental transformation in organic synthesis that converts a C–H bond to a C–X bond. Traditionally, radical halogenation has been accomplished using harsh reaction conditions like ultraviolet light and toxic reagents. In this research, we are exploring a new, more sustainable approach to radical halogenation using photocatalysis. Specifically, we are investigating the radical halogenation of organic molecules using the photocatalyst tetra-n-butylammonium decatungstate (TBADT) and a variety of halogen sources. In the presence of light, TBADT becomes excited and abstracts a hydrogen atom from the starting material to form an alkyl radical. The radical intermediate may then abstract a halogen atom from the halogen source to form a C–X bond. Optimization of the reaction conditions revealed diethyl bromomalonate as a promising bromine source for radical bromination in combination with the TBADT catalyst. Preliminary substrate scope investigations show that a variety of C–H bonds, both activated and inactivated, can be brominated using this method. The selectivity of the radical bromination was also explored.