Fig. 1: Relevance and chemistry of azetidines and ABBs.
From: Radical strain-release photocatalysis for the synthesis of azetidines

a, Relevance of the azetidine scaffold and current prevalence in approved drugs. b, Selected examples of drugs featuring the azetidine core. c, Available synthetic strategies for constructing the azetidine core. d, Development of a RSR synthetic method, and the general mechanism of the synthesis.