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

aibn cycling

B) In this second example we will take advantage of the reactivity of the nitrenes through the carbon-nitrogen insertion to obtain the carbazole.

carbazole synthesis

C) Synthesis of indole from azide, via nitrene.

indole synthesis via nitrene

D) Cyclization processes via carbenes

synthesis via carbenes