C(sp3)−H Functionalization Using Chlorine Radicals

Abstract Converting any desired C−H bond to the intended C−Z bond in a given organic molecule could be the final peak of the C−H functionalization methodology. Among the three types of C−H bonds, the functionalization of the ubiquitous C( sp 3 )−H bond has gained particular attention, especially in the last two decades. There are different ways to transform C( sp 3 )−H bonds into desired C−Z bonds. The use of chlorine radicals is one of these methods with a promising future. The literature review shows that different sources have been used for chlorine, including chloride ions (HCl or chloride salts), coordinated chlorides (transition metal complexes), and organic chlorides (organochlorine compounds). However, HCl and FeCl 3 have gained the most attention among these sources. There are three major ways to convert chlorine from these sources to chlorine radicals: 1) oxidation of hydrogen chloride or chloride salts, 2) photolysis of metal chloride, and 3) transition metal insertion into C−Cl bonds. This review summarizes published research papers on the use of chlorine radicals for C( sp 3 )−H bonds functionalization. Therefore, chlorination reactions of C( sp 3 )−H bonds and reactions in which chlorine radicals do not play a direct role in C( sp 3 )−H bond cleavage are not within the scope of this review.