Scalable anti-Markovnikov hydrobromination of aliphatic and aromatic olefins

Org Biomol Chem. 2016 Jun 28;14(24):5622-6. doi: 10.1039/c6ob00692b. Epub 2016 May 17.

Abstract

To improve access to a key synthetic intermediate we targeted a direct hydrobromination-Negishi route. Unsurprisingly, the anti-Markovnikov addition of HBr to estragole in the presence of AIBN proved successful. However, even in the absence of an added initiator, anti-Markovnikov addition was observed. Re-examination of early reports revealed that selective Markovnikov addition, often simply termed "normal" addition, is not always observed with HBr unless air is excluded, leading to the rediscovery of a reproducible and scalable initiator-free protocol.