Meerwein arylation

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.

[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.

[5] In a so-called reductive arylation with 3-buten-2-one, titanium trichloride reduces the newly formed double bond.