Synthesis of Cycloheptatriene-Containing Azetidine Lactones

Area of Science:

• Organic Chemistry
• Photochemistry
• Synthetic Chemistry

Background:

• Photolysis of phenacyl amines typically results in charge transfer and elimination.
• Protonation strategies can alter reaction pathways and outcomes in photochemical processes.

Purpose of the Study:

• To synthesize complex cycloheptatriene-containing azetidine lactones.
• To investigate the mechanisms of aza-Yang cyclization and Buchner carbene insertion.
• To explore the influence of amine protonation on azetidinol formation.

Main Methods:

• Utilized photochemical aza-Yang cyclization and Buchner carbene insertion reactions.
• Employed ultrafast spectroscopy to study excited-state electron transfer.
• Investigated reaction kinetics and diastereoselectivity.

Main Results:

• Successfully prepared 16 novel cycloheptatriene-containing azetidine lactones over seven steps.
• Demonstrated diastereoselective formation of azetidinols via protonated amines.
• Identified the dependence of aza-Yang reaction rates on photon absorption.
• Explained reactivity changes in morpholine analogues through tosylate anion interactions.
• Buchner reaction showed slight diastereomer preference, requiring electron-donating substituents.

Conclusions:

• Developed a synthetic route to complex azetidine lactones using photochemistry.
• Protonation is key for achieving diastereoselective azetidinol synthesis.
• These findings expand the accessible chemical space for novel compound discovery.