Benzylic Bromination with Bromotrichloromethane

Abstract

The benzylic bromination of alkyl groups attached to aromatic nuclei is most often accomplished with N-bromosuccinimide (NBS) and a free radical initiator² Alternatively molecular bromine and a free radical initiator have also been employed.³ When the aromatic ring is activated by electron donating groups, both of these methods often lead to nuclear bromination as the predominant product; in some cases literature results have proved difficult to duplicate. For instance, although it is reported that NBS bromination of m-methoxytoluene affords the benzylic bromide in good yield,⁴ we have obtained only nuclear bromination under a variety of reaction conditions.