Japp-Klingemann Fischer indole synthesis

What is Japp-Klingemann Fischer indole synthesis?

The Japp-Klingemann reaction and Fischer indole synthesis can be combined to create a reaction that involves the condensation of an aryldiazonium salt with an active methylene or methinyl compound. This condensation occurs under either acidic or basic conditions and leads to the formation of a hydrazone derivative. Subsequently, cyclization occurs to give a substituted indole product.

Japp-Klingemann Fischer indole synthesis - general reaction scheme - Japp-Klingemann Fischer indole protocol - the Japp-Klingemann/Fischer indole process -the Japp-Klingemann Fischer indole synthesis - the Japp-Klingemann indole synthesis - Japp-Klingemann indole formation
Japp-Klingemann Fischer indole synthesis
  • R1 = Me
  • R2, R3 = alkyl, aryl

This reaction is known by various names, such as the Japp-Klingemann Fischer indole protocol, the Japp-Klingemann/Fischer indole process, the Japp-Klingemann Fischer indole synthesis, or the Japp-Klingemann indole synthesis or Japp-Klingemann indole formation. The reaction was likely first described by Findlay and Dougherty in 1948, who aimed to avoid the use of arylhydrazines, which can be challenging to prepare and handle in some cases.

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