Borsche–Drechsel cyclization

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Borsche–Drechsel cyclization
Named after Walter Borsche
Edmund Drechsel
Reaction type Ring forming reaction
RSC ontology ID RXNO:0000532

The Borsche–Drechsel cyclization is a chemical reaction used to synthesize tetrahydrocarbazoles by the acid-catalyzed cyclization of cyclohexanone arylhydrazones. The reaction is was first described by Edmund Drechsel in 1888[1] and by Walter Borsche in 1908.[2]

Borsche–Drechsel cyclization

Borsche–Drechsel cyclization is the central step in Borsche–Drechsel carbazole synthesis, where in the first step phenylhydrazine is condensed with cyclohexanone to form the cyclohexanone phenylhydrazone, and in the final step the resulting tetrahydrocarbazole is oxidized to carbazole itself.

Borsche–Drechsel carbazole synthesis


  1. ^ E. Drechsel (1888). "Ueber Elektrolyse des Phenols mit Wechselströmen". J. prakt. Chem. (in German). 38 (1): 65–74. doi:10.1002/prac.18880380105. 
  2. ^ W. Borsche (1908). "Ueber Tetra- und Hexahydrocarbazolverbindungen und eine neue Carbazolsynthese. (Mitbearbeitet von. A. Witte und W. Bothe.)". Justus Liebigs Ann. Chem. (in German). 359 (1–2): 49–80. doi:10.1002/jlac.19083590103. 

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