Synthesis, Reactions and Medicinal Uses of Acridine

Acridine

Synthesis

Bernthsen acridine synthesis - In the presence of zinc chloride, diphenylamine condenses with carboxylic acids to form acridines.


From o-chlorobenzene acid - A diphenylamine-2-carboxylic acid is formed by condensing aniline and o-chlorobenzene acid. Using POCl3 as a catalyst, this acid gives 9-chloroacridine.


Acridine is formed after the hydrogenation of 9-chloroacridine is followed by the oxidation of the chloride with ferric chloride.


Condensation of diphenylamine with chloroform along with alkyl chloride gives acridine.



Friedlander synthesis - At 120°C, cyclohexane-2-enone is treated with salt of anthranilic acid to produce 9-methyl acridine.


From C – acylated diphenylamine - A first acylation is performed on diphenylamine. A thermochemical reaction produces 9-phenylacridine by heating acylated diphenylamine in presence of I2/HI.

Reactions

Anathracene's aza derivative is acridine. It acts as a weak base. Acridine is chemically similar to pyridine and quinoline as it has one electron available on the N-atom and has an aromatic nature.

N – protonation - Since acridine is a weak acid, its lone electron pairs make it form soluble salts when protonated at a N-atom. A first protonation of the ring N-atom occurs in amino-acridine, resulting in a double salt.



Electrophilic substitution - A benzenoid ring is attacked by the electrophile preferably in the 2- or 7-position, resulting in di-substitution. For example,

Nucleophilic substitution - Nucleophilic reagents interact more strongly with quaternary salts of acridine. Compared with positions 1-, 2-, 3- and 4-, position-9 of acridine has a low electron density. Therefore, nucleophiles prefer to attack at 9-position.


Oxidation - During dichromate oxidation in acetic acid, acridine becomes acridone. Quinoline -2, 3-dicarboxylic acid is formed by oxidative ring cleavage carried out by KMnO4 in alkaline media.


Reduction - By catalytic hydrogenation, the benzene rings in acridine can be selectively reduced while the pyridine ring can be selectively reduced by zinc/hydrochloride to give 9, 10-dihydroacridine.




Reduction alkylation - Upon exposure to ultraviolet light, acridine combines with n-pentanoic acid to form 9-n-butylacridine.

Medicinal Uses

Acridine is a key component in many drugs on the market. There are a number of drugs that may be considered anaesthetics: bucricaine (anesthetic), quinacrine (or mepacrine: antimalaria), 9-ammoacridine (disinfectant), proflavin (antibacterial), nitracine (anti-cancer), acriflavine (antiseptic), etc.

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