Intramolecular SN2 -type reactions are a powerful tool to form 5, 6, and 3-membered cycles, resulting slow in 4- and 7-membered cyclizations. These are concerted and stereospecific reactions, which further increases their synthetic value.
i) Formation of aziridine.
ii) Formation of oxirane by Darzens reaction.
[1] Hydrogen alpha subtraction from ester
[2] Nucleophilic addition to carbonyl
[3] Intramolecular nucleophilic substitution
iii) Formation of azetidine.
Mechanism:
iv) Oxazole formation
Mechanism:
