Carbazole

From DrugPedia: A Wikipedia for Drug discovery

Carbazole is an aromatic heterocyclic organic compound. It has a tricyclic structure, consisting of two six-membered benzene ring fused on either side of a five-membered nitrogen-containing ring. The compound's structure is based on the indole structure but in which a second benzene ring is fused onto the five-membered ring at the 2-3 position of indole (equivalent to the 4a-9a double bond in carbazole).

A classic laboratory organic synthesis for carbazole is the Borsche-Drechsel cyclization In the first step phenylhydrazine is condensed with cyclohexanone to the corresponding imine. The second step is a hydrochloric acid catalyzed rearrangement reaction and ring-closing reaction to tetrahydrocarbazole. In one modification both steps are rolled into one by carrying out the reaction in acetic acid. In the third step this compound is oxidized by Red lead to carbazole itself. Another classic is the Bucherer carbazole synthesis.

A second method for the synthesis of Carbazol is the Graebe-Ullmann reaction. In a first step a N-phenyl-1,2-diaminobenzene (N-phenyl-o-phenylenediamine) is converted into a diazoniumsalt which instantaniuosly forms a 1,2,3-triazole. The triazole is unstable and at elevated temperatures nitrogen is set free and the carbazole is formed.

Safety information for carbazole, from the Chemistry Department at Oxford University, is available here.