Meerwein arylation

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Meerwein arylation

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Meerwein arylation is a chemical reaction used in organic chemistry to form aryl-substituted alkenes from diazonium salts and alkenes. This reaction is named after the German chemist Hans Meerwein, who first reported it in the early 20th century.

Reaction Mechanism

The Meerwein arylation involves the reaction of a diazonium salt with an alkene in the presence of a copper(I) salt, typically copper(I) chloride or copper(I) bromide. The general mechanism proceeds as follows: 1. Formation of Diazonium Salt: An aniline derivative is treated with nitrous acid to form the corresponding diazonium salt. 2. Generation of Aryl Radical: The diazonium salt undergoes homolytic cleavage in the presence of a copper(I) salt to generate an aryl radical. 3. Addition to Alkene: The aryl radical adds to the alkene, forming a new carbon-carbon bond. 4. Termination: The resulting radical intermediate is terminated by abstraction of a hydrogen atom or by coupling with another radical.

Applications

Meerwein arylation is used in the synthesis of various organic compounds, particularly in the formation of styrene derivatives and other aryl-substituted alkenes. It is valuable in the field of pharmaceutical chemistry for the construction of complex molecular architectures.

Advantages and Limitations

Advantages

• The reaction provides a straightforward method to introduce aryl groups into alkenes.
• It can be performed under relatively mild conditions.

Limitations

• The reaction often requires the use of stoichiometric amounts of copper salts, which can be a drawback in terms of cost and environmental impact.
• The scope of the reaction can be limited by the stability of the diazonium salt and the reactivity of the alkene.

See Also

• Diazonium compound
• Radical reaction
• Copper-catalyzed reactions
• Hans Meerwein