The Synthetic Routes of N,N,N′,N′-Tetraphenylbenzidine

N,N,N′,N′-Tetraphenylbenzidine (TPB) is a commonly used reagent in organic synthesis and is widely used in various applications in the chemical industry.
It is a yellow or orange crystalline solid that is soluble in organic solvents.
TPB is used as a ligand in coordinate chemistry, as a catalyst for the polymerization of monomers, and as a phosphorescent material in organic light-emitting diodes (OLEDs).

One of the most common synthetic routes for TPB involves the reduction of 4-chloro-1,2-phenylenediamine with sodium in the presence of a base such as triethylamine.
The resulting intermediate is then nitrated with nitric acid to form N,N′-dinitro-N,N′-dihydro-2,6-dimethylphenylbenzidine, which is then reduced with hydrogen in the presence of a metal catalyst such as palladium on barium oxide to form TPB.

Another synthetic route for TPB involves the condensation of 1,2-dimethyl-1,2-phenylenediamine with 4-chloroaniline in the presence of a solvent such as N,N-dimethylacetamide.
The resulting intermediate is then nitrated with nitric acid and reduced as described above to form TPB.

In recent years, there has been a growing interest in the development of alternative, more efficient synthetic routes for TPB.
One such route involves the reaction of 4-chloro-1,2-phenylenediamine with sodium dithiocarbamate in the presence of a base such as triethylamine.
The resulting intermediate is then nitrated with nitric acid and reduced as before to form TPB.
This route offers several advantages over the traditional routes, including a lower reaction temperature, a shorter reaction time, and the use of less expensive and more readily available reagents.

Another alternative synthetic route for TPB involves the reaction of 4-chloro-1,2-phenylenediamine with 2-chloro-1-nitro-4-phenyl-butane in the presence of a solvent such as toluene.
The resulting intermediate is then reduced with hydrogen in the presence of a metal catalyst such as palladium on barium oxide to form TPB.

Overall, N,N,N′,N′-tetraphenylbenzidine is a versatile and important reagent in organic synthesis, and there are several synthetic routes available for its preparation.
These routes offer a range of advantages, including lower reaction temperatures, shorter reaction times, and the use of less expensive and more readily available reagents.
As the demand for TPB continues to grow, it is likely that new and more efficient synthetic routes will be developed to meet this demand.