Site Selective Chlorination of C(sp³)−H Bonds Suitable for Late‐Stage Functionalization

Abstract C(sp 3 )−Cl bonds are present in numerous biologically active small molecules, and an ideal route for their preparation is by the chlorination of a C(sp 3 )−H bond. However, most current methods for the chlorination of C(sp 3 )−H bonds are insufficiently site selective and tolerant of functional groups to be applicable to the late‐stage functionalization of complex molecules. We report a method for the highly selective chlorination of tertiary and benzylic C(sp 3 )−H bonds to produce the corresponding chlorides, generally in high yields. The reaction occurs with a mixture of an azidoiodinane, which generates a selective H‐atom abstractor under mild conditions, and a readily‐accessible and inexpensive copper(II) chloride complex, which efficiently transfers a chlorine atom. The reaction's exceptional functional group tolerance is demonstrated by the chlorination of >30 diversely functionalized substrates and the late‐stage chlorination of a dozen derivatives of natural products and active pharmaceutical ingredients.