A Closer Look at the Bromine–Lithium Exchange with tert-Butyllithium in an Aryl Sulfonamide Synthesis

A practical protocol for the one-pot synthesis of various aryl sulfonamides, notably of pyridine-core-substituted 7-azaindolyl sulfonamides, is described. A key step is the well-known bromine–lithium exchange reaction of an aryl bromide with tert-butyllithium (t-BuLi). Differing from the common practice to use 2 or more equiv of organolithium, the exact amount of t-BuLi needed for a sufficient exchange reaction is determined for each aryl bromide in a GC–MS-assisted experiment.