Functionalized oxepines via fragmentation of highly strained epoxides

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Stereochemistry

Background:

• Cyclobutene derivatives are highly strained cyclic alkenes.
• Thermal rearrangements are common synthetic transformations in organic chemistry.
• Oxepines are seven-membered oxygen-containing heterocycles.

Purpose of the Study:

• To investigate the epoxidation of highly strained cyclobutenes.
• To explore the thermal rearrangement of these epoxides.
• To synthesize novel oxepine-containing bicyclo[5.3.0] ring systems.

Main Methods:

• Epoxidation of strained cyclobutenes using suitable oxidizing agents.
• Thermal treatment of the resulting epoxides to induce rearrangement.
• Analysis of reaction products to determine structure and stereochemistry.

Main Results:

• Successful epoxidation of highly strained cyclobutenes.
• Thermal rearrangement leads to the formation of bicyclo[5.3.0] ring systems containing an oxepine moiety.
• Two competing fragmentation pathways were observed, leading to diastereomeric products.
• The observed pathways differ from those seen in analogous cyclopropanated systems.

Conclusions:

• Epoxidation followed by thermal rearrangement is a viable route to oxepine-containing bicyclo[5.3.0] systems.
• The fragmentation mechanism of these strained epoxides is complex, involving competing pathways.
• Stereochemical outcomes are influenced by the specific rearrangement and fragmentation processes.