30984-15-7Relevant articles and documents
The concerted addition of HBr to aryl alkynes; orthogonal pi bond selectivity
Weiss, Hilton M.,Touchette, Kim M.,Angell, Sarah,Khan, Jihan
, p. 2152 - 2156 (2007/10/03)
In a weakly acidic solution, the addition of HBr to 1-phenylprop-1-yne produces predominantly the anti-Markovnikov product. In this paper, we consider five possible explanations for this behavior and conclude that the concerted addition is occurring on the acetylenic π bond orthogonal to the extended aromatic π system. The electronic effect of the distal methyl group and the steric hindrance of the coplanar phenyl ring combine to promote bromide attack at the β carbon. Attack on this π bond is insensitive to the electronic effect of meta and para substituents on the ring but is very (sterically) sensitive toward all ortho substituents.
