1-Bromo-4-iodobenzene

1-Bromo-4-iodobenzene is a mixed aryl halide (aryl bromide and aryl iodide) with the formula BrC6H4I.

Preparation
In one laboratory route to 1-bromo-4-iodobenzene, 4-bromoaniline is treated with concentrated sulfuric acid and sodium nitrite to form the diazonium salt, which is then treated with potassium iodide to form 1-bromo-4-iodobenzene.

Reactions
Since aryl iodides are more reactive than aryl bromides in the Sonogashira coupling, the iodine end of 1-bromo-4-iodobenzene can be selectively coupled to a terminal acetylene while leaving the bromine end unreacted, by running the reaction at room temperature. For example, two equivalents of 1-bromo-4-iodobenzene can couple to trimethylsilylacetylene in a room temperature symmetrical Sonogashira coupling (with TMSA being deprotected to acetylene in-situ) to form bis(4-bromophenyl)acetylene.
 * [[Image:Symmetrical sonogashira 1-bromo-4-iodobenzene.png|600px|Symmetrical Sonogashira coupling of 1-bromo-4-iodobenzene with trimethylsilylacetylene with in situ TMSA deprotection.]]