a) Leaving groups near the ring
Indole throws out to the outgoing groups located in the neighboring situation to a ring. In addition, it is necessary that the chain that has the leaving group is located in position 3 of the ring.
b) Carboxylic acids
The carboxylic group, both in position 2 and 3, decarboxylates on heating.
c) Hydroxy derivatives
The 2- and 3-hydroxy derivatives of the indole tautomerize to the keto form.
