The bromination of substituted 3-arylpropynes in acetic acid has been examined. The only products obtained are 1, 2-dibromo-3-arylpropenes; the stereochemistry of the dibromides is predominantly trans except for the 4-methoxy isomer which gives 83% cis and 17% trans. In the presence of 0.1 M lithium bromide all substrates give predominantly trans products. Combined with rate studies, these results indicate that these acetylenes react by an ...
