Stereochemistry of polymethylated β,β′-dibromoethers formed by bromination of alkene–epoxide mixtures

Examination of β,β′-dibromoethers formed when bromine is added to alkene–epoxide mixtures in pentane at –78 °C revealed that opening of the bromonium ion and the epoxide occurs under high stereochemical control, whilst approach of the epoxide and the bromonium ion is subject to lower or no stereochemical control.