Hoesch reaction

The Houben- Hoesch reaction, also known as the Hoesch synthesis, Hoesch reaction, Houben -Hoesch - Houben -Hoesch acylation or synthesis, is a name reaction in organic chemistry. The reaction is named after Kurt Hoesch (1882-1932), who published them in 1915, and after Josef Houben ( 1875 to 1940 ) (Publication 1926). By the reaction of electron-rich aromatic compounds can be acylated.

Overview reaction

Electron-rich aromatic compounds such as phenols with more hydroxyl groups or corresponding ether ( here exemplified with resorcinol ) can be acylated with organic nitriles in the presence of hydrogen chloride and a Lewis acid (such as AlCl3 or ZnCl2 ).

Mechanism

The mechanism is shown in the example of the reaction between a 1,3- dihydroxybenzene ( resorcinol ) with a general organic nitrile. As Lewis acid example aluminum chloride ( AlCl3 ) is utilized.

First, the nitrile 1 forms a complex with aluminum chloride and 2 with another aluminum chloride complex to the 3 This complex will react with resorcinol in the course of electrophiles aromatic substitution through the intermediate step of 4 to 5 molecules, wherein AlCl 3 leaves the molecule. To the molecule 4 additional resonance structures can be drawn, which correspond to the boundary structures in the course of a third substitution. The reaction with water leads to further elimination of the Lewis acid aluminum chloride. The molecule 6 finally reacts with hydrogen chloride to the ketone 7, which is in this case the acylated resorcinol.