Strained rings are significant structures with versatile applications in organic chemistry. A lot of efforts have been attracted to their transformations and pharmaceutical properties. Four-membered rings have less ring-strain than their three-membered counterparts. Therefore, their opening requires comparably harsh conditions. However, those reactions are significant in organic synthesis. As important four-membered rings, oxetanes and azetidines have been demonstrated to be particularly useful in asymmetric synthesis.

In Chapter 1, the conversion of oxetane-containing anilines to 1,2-dihydroquinolines via intramolecular cyclization is described. The reaction was found as an unexpected outcome of an initial design. After careful optimization, a series of substrates underwent t...[ Read more ]

Strained rings are significant structures with versatile applications in organic chemistry. A lot of efforts have been attracted to their transformations and pharmaceutical properties. Four-membered rings have less ring-strain than their three-membered counterparts. Therefore, their opening requires comparably harsh conditions. However, those reactions are significant in organic synthesis. As important four-membered rings, oxetanes and azetidines have been demonstrated to be particularly useful in asymmetric synthesis.

In Chapter 1, the conversion of oxetane-containing anilines to 1,2-dihydroquinolines via intramolecular cyclization is described. The reaction was found as an unexpected outcome of an initial design. After careful optimization, a series of substrates underwent the desired reactions in good yields, and the afforded products were transformed to useful structures in effective ways. Regarding the mechanism, the reaction might involve a range of bond cleavage and formation steps. This work not only provides a new method to synthesize 1,2-dihydroquinolines, but also reveals the unusual reactivity of oxetane-containing anilines.

In Chapter 2, a copper-catalyzed ring expansion of azetidines to pyrrolidines is disclosed. This reaction enriches the routes to pyrrolidines from azetidines. The suitable use of an aryl substituent on the nitrogen is important for the reactivity of substrates. Preliminary scope studies have been made, and the two possible pathways the reaction might proceed through was proposed.