A Oxidative Bromination of (Hetero)Arenes in the TMSBr/DMSO System: A Non-Aqueous Procedure Facilitates Synthetic Strategies

摘要

An oxidative bromination protocol for aromatic compounds using trimethylsilyl bromide (TMSBr) and DMSO has been developed. This mild bromination system tolerates a wide variety of functionalities including amide, aldehyde, ester and acetal groups. Arylbromides and heteroarylbromides are produced in up to 95% yield at 25 8C. Arenes bearing electrondonating groups are selectively brominated at the para position unless it is blocked. The highlight of this protocol consists in its non-aqueous conditions, which are fruitful particularly in the context of integrated synthetic systems. The utility of this method was demonstrated with three examples, in either of which the bromination was followed by another reaction: a “click” triazole formation, a Suzuki–Miyaura crosscoupling, or an aldehyde formation via lithium–bromine exchange, without the isolation of the bromide intermediate in any case. It is particularly remarkable for this non-aqueous protocol to allow lithiation reactions to sequentially follow the bromination.