Synthesis of Thietanes from Saturated Three-membered Heterocycles

Thietanes are important structural motifs of some biological compounds and useful intermediates in organic synthesis. Various synthetic methods of thietanes have been developed recently with readily available saturated three-membered heterocycles as starting materials or key intermediates. Both saturated three membered heterocycle-2-methyl halides and sulfonates and thiiranes are widely utilized materials. Both nucleophilic and electrophilic ring expansions of thiiranes are efficient methods for synthesis of thietanes. In this Focus Review, we have described various strategies for the synthesis of strained four-membered thiaheterocyclic thietanes from readily available strained and saturated three-membered heterocycles.