Illustrative is the reaction of the weakly basic secondary amine carbazole with formaldehyde. It is produced by the vinylation of carbazole with acetylene in the presence of base. Another classic is the Bucherer carbazole synthesis. Some species also contain the carbazole girinimbine. The Bucherer carbazole synthesis is a related reaction. In the third step, this compound is oxidized by red lead to carbazole itself. Carbazole is an aromatic heterocyclic organic compound. Carbazole is a constituent of tobacco smoke. Carbazole was also used in the same literature entry. Carbazole can be denitrogenated by hydrogen to yield bicyclohexyl as the main product.