There might be more recent publications, but an old review by Robert G. Johnson and Robert K. Ingham, Chem. Rev., 1956, 56, 219-269, gives some
directions.
Based on early attempts with benzoic acid that date back to the time around 1840, is was long believed that the silver salts of aromatic carboxylic
acids do not undergo a Hunsdiecker reaction at all. The authors write:
In no case was bromobenzene obtained as a result of the action of bromine on silver benzoate. The product of Peligot and Bunge was a monobromobenzoic
acid; apparently Kekule’s experiment was completely unsuccessful.
However, it later turned out that the inital verdict wasn't quite true.
Benzoic acids bearing electron-withdrawing substituents, such as Cl or NO2 can be converted to their corresponding bromoarenes in a Hunsdiecker
reaction. The authors of the review denote:
Thus, the three isomeric nitrobenzoic acids (as silver salts) were converted to the corresponding bromides in excellent yields (ortho, 95 per cent;
meta, 89 per cent; para, 79 per cent). The yields from the chlorobenzoic acids were less satisfactory, but sufficiently high to indicate the efficacy
of the chloro group. |
