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.

aziridine formation

ii) Formation of oxirane by Darzens reaction.

oxirane formation

[1] Hydrogen alpha subtraction from ester

[2] Nucleophilic addition to carbonyl

[3] Intramolecular nucleophilic substitution


iii) Formation of azetidine.

azetidine formation 01


azetidine formation mechanism

iv) Oxazole formation

oxazole formation


oxazole formation mechanism