Meerwein_arylation
Meerwein arylation
Organic reaction
The Meerwein arylation is an organic reaction involving the addition of an aryl diazonium salt (ArN2X) to an electron-poor alkene usually supported by a metal salt.[1] The reaction product is an alkylated arene compound. The reaction is named after Hans Meerwein, one of its inventors who first published it in 1939.
An electron-withdrawing group (EWG) on the alkene makes it electron deficient and although the reaction mechanism is unclear,[2] involvement of an aryl radical is presumed after loss of nitrogen in the diazonium salt followed by a free radical addition. In the primary reaction product the intermediate alkyl radical is then captured by the diazonium counterion X which is usually a halogen or a tetrafluoroborate. In a subsequent step an elimination reaction liberates HX (for instance hydrochloric acid) and an aryl vinyl compound is formed. The reaction mechanism from the arene's view ranks as a radical-nucleophilic aromatic substitution.
In a general scope a Meerwein arylation is any reaction between an aryl radical and an alkene.[3] The initial intermediate is an aryl enthenyl radical which can react with many trapping reagents such as hydrogen or halogens or with those based on nitrogen or sulfur.