In this section we will see examples of cyclizations that take place through intermediates of radical type, carbene or nitrene.
A) We begin with a radical cyclization, which uses tributyltin hydride as a reagent and is initiated by AIBN
Mechanism:
1. initiation
2. Propagation
B) In this second example we will take advantage of the reactivity of the nitrenes through the carbon-nitrogen insertion to obtain the carbazole.
Mechanism:
C) Synthesis of indole from azide, via nitrene.
Mechanism:
D) Cyclization processes via carbenes
Mechanism: