Japp-Maitland condensation

What is Japp-Maitland condensation?

In 1903, Japp and Maitland were the first to report a reaction known as the Japp-Maitland condensation, not to be confused with Maitland-Japp reaction. This reaction involves the acid-promoted thermal condensation between arylhydrazine and aromatic compounds that are activated by a hydroxyl group.

Japp-Maitland condensation - general reaction scheme - Maitland-Japp reaction
Japp-Maitland condensation

The product of this reaction is a carbazole derivative. For instance, the condensation of 6-alkyl-2-naphthols with phenylhydrazine yields 3-alkyl-7H-benzo-[c]carbazoles in high yield.

However, the use of naphthylhydrazines and their salts is limited due to their heat sensitivity, resulting in very low yields of corresponding carbazoles. Moreover, the reaction with simple 2-naphthol also leads to poor yields.