Phenanthridine is a nitrogen heterocyclic compound that is the basis of DNA-binding fluorescent dyes through intercalation

Intercalation

Intercalation is the insertion of a leap day, week or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.- Solar calendars :...

. Examples of such dyes are ethidium bromide

Ethidium bromide

Ethidium bromide is an intercalating agent commonly used as a fluorescent tag in molecular biology laboratories for techniques such as agarose gel electrophoresis. It is commonly abbreviated as "EtBr", which is also an abbreviation for bromoethane...

 and propidium iodide

Propidium iodide

Propidium iodide is an intercalating agent and a fluorescent molecule with a molecular mass of 668.4 Da that can be used to stain cells. When excited with 488 nm wavelength light, it fluoresces red...

. Acridine

Acridine

Acridine, C13H9N, is an organic compound and a nitrogen heterocycle. Acridine is also used to describe compounds containing the C13N tricycle....

 is an isomer of phenanthridine.

Phenanthridine was discovered by Amé Pictet

Amé Pictet

Amé Pictet was a Swiss chemist. He discovered the Pictet-Spengler reaction.Pictet was born in Geneva, studied with August Kekulé at the University of Bonn where he received his Ph.D in 1879. From 1894 til 1932 he was professor at the University of Geneva. Pictet died in Geneva in 1937.-External...

 and H. J. Ankersmit in 1891 by pyrolysis

Pyrolysis

Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...

 of the condensation product of benzaldehyde

Benzaldehyde

Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...

 and aniline

Aniline

Aniline, phenylamine or aminobenzene is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane...

 . In the Pictet-Hubert reaction (1899) the compound is formed in a reaction of the 2-aminobiphenyl - formaldehyde adduct (an N-acyl-o-xenylamine) with zinc chloride

Zinc chloride

Zinc chloride is the name of chemical compound with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. ZnCl2 itself is hygroscopic and even deliquescent. Samples should therefore be protected from...

 at elevated temperatures . The reaction conditions were improved by Morgan and Walls in 1931, replacing the metal by phosphorus oxychloride and using nitrobenzene

Nitrobenzene

Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale as a precursor to aniline. Although occasionally used as a flavoring or perfume...

 as a reaction solvent . For this reason the reaction is also called the Morgan-Walls reaction .

The reaction is similar to the Bischler–Napieralski reaction and the Pictet–Spengler reaction.