Catalytic Halogen Bond Activation in the Benzylic C–H Bond Iodination with Iodohydantoins

This letter presents the side-chain iodination of electron-deficient benzylic hydrocarbons at rt using N-hydroxyphthalimide (NHPI) as radical initiator and 1,3-diiodo-5,5-dimethylhydantoin and 3-iodo-1,5,5-trimethylhydantoin (3-ITMH) as iodine source. Addition of a carboxylic acid increased the reactivity due to complex formation with and activation of 3-ITMH by proton transfer and halogen bond formation. No SEAr reactions were observed under the employed reaction conditions. Our method enables convenient product isolation and gives 50–72% yields of isolated products.