Demjanov rearrangement

Demjanov Rearrangement is a significant chemical reaction that involves the transformation of primary amines into alcohols through the intermediacy of nitrous acid. This reaction is named after the Russian chemist Nikolai Jakovlevich Demjanov, who first reported it in the early 20th century. The Demjanov rearrangement is notable for its application in the synthesis of alcohols from amines, which are themselves readily obtainable from aldehydes and ketones. This reaction is particularly useful in organic synthesis and has been employed in the preparation of various complex molecules.

Mechanism

The Demjanov rearrangement begins with the conversion of a primary amine to a nitroso compound through treatment with nitrous acid, which is typically generated in situ from sodium nitrite and a mineral acid. The nitroso compound then undergoes tautomerization to form a hydroxylamine, which, upon further reaction with nitrous acid, generates a diazonium ion. This highly reactive species then undergoes a 1,2-rearrangement, where the alkyl group migrates to the neighboring nitrogen atom, resulting in the formation of an alcohol after hydrolysis.

Variants

A notable variant of the Demjanov rearrangement is the Tiffeneau-Demjanov rearrangement, which involves the ring expansion of cyclic amines to form larger ring systems. This variant is particularly useful for the synthesis of cyclic compounds with one additional ring member.

Applications

The Demjanov rearrangement has found applications in the synthesis of complex natural products and pharmaceuticals. Its ability to efficiently convert amines into alcohols makes it a valuable tool in the arsenal of organic chemists. The reaction has been utilized in the synthesis of various compounds, including steroids, alkaloids, and terpenes.

Limitations

Despite its utility, the Demjanov rearrangement has some limitations. The reaction conditions can sometimes lead to side reactions, including the over-oxidation of the product alcohol to a carbonyl compound. Additionally, the reaction's applicability is somewhat limited by the stability of the starting amine and the generated diazonium ion.

See Also

• Amine
• Alcohol
• Nitrous acid
• Diazonium compound
• Organic synthesis
• Tiffeneau-Demjanov rearrangement