Bischler–Möhlau indole synthesis

The Bischler–Möhlau indole synthesis is a chemical reaction that forms a 2-aryl-indole from an α-bromo-acetophenone and excess aniline; it is named after August Bischler and Richard Möhlau ^{[1][2][3][4][5]}

In spite of its long history, this classical reaction has received relatively little attention in comparison with other methods for indole synthesis, perhaps owing to the harsh reaction conditions that it requires. Recently, milder methods have been developed, including the use of lithium bromide as a catalyst and an improved procedure involving the use of microwave irradiation.^[6][7][8]

Reaction mechanism

The first two step involve the reaction of the α-bromo-acetophenone with molecules of aniline to form intermediate 4. The charged aniline forms a decent enough leaving group for an electrophilic cyclization to form intermediate 5, which quickly aromatizes and tautomerizes to give the desired indole 7.

See also

• Fischer indole synthesis
• Bischler–Napieralski reaction

References