Wagner-Jauregg reaction
{{Short description|Chemical reaction}}
The Wagner-Jauregg reaction is a classic organic reaction in organic chemistry, named after {{ill|Theodor Wagner-Jauregg|de}} (son of Julius Wagner-Jauregg), describing the double Diels–Alder reaction of 2 equivalents of maleic anhydride with a 1,1-diarylethylene. After aromatization of the bis-adduct, the ultimate reaction product is a naphthalene compound with one phenyl substituent.{{cite journal | author = Theodor Wagner-Jauregg | journal = Berichte der Deutschen Chemischen Gesellschaft (A and B Series)| volume = 68 | pages = 3218 | year = 1930 | doi = 10.1002/cber.19300631140 | title = Über addierende Hetero-polymerisation | issue = 11}}{{cite journal | author = Theodor Wagner-Jauregg | journal = Justus Liebig's Annalen der Chemie| volume = 491 | pages = 1–13 | year = 1931 | doi = 10.1002/jlac.19314910102 | title = Die Addition von Maleinsäureanhydrid an asymm. Diphenyl-äthylen}}
The reaction is unusual in that the anhydride reacts with the aromatic ring. The presence of the additional alpha-phenyl group on the phenylethene (the styryl group) activates the styryl for a Diels–Alder reaction even at the expense of its aromaticity. In contrast, unactivated styrene reacts instead at the alkene alone via a linear polymerization reaction. Styrene maleic anhydride copolymer is formed, retaining the aromaticity of the styrene.
The Diels–Alder product can be re-aromatized using elemental sulfur at high temperature, followed by a second rearomatization by decarboxylation with barium hydroxide and copper:{{cite journal | title = The Condensation of 1,1-Diarylethylenes with Maleic Anhydride |author1=Felix Bergmann |author2=Jacob Szmuszkowicz |author3=George Fawaz |name-list-style=amp | journal = Journal of the American Chemical Society | year = 1947 | volume = 69 | issue = 7 | pages = 1773–1777 | doi = 10.1021/ja01199a055 | pmid=20251415}}
