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cyclobutadiene cycloadditions with imines
[2+2+1] Cycloadditions
Cacospongionolide B
5-8-5 Ring Systems
5-7 Ring Systems
Tandem Methathesis Olefin Isomerization
Catalytic Asymmetric Synthesis of Amines


5-8-5 Ring Systems

Researchers - Priscilla Lo, Sean McCarthy

Priscilla LoDicyclopenta[a,d]cyclooctene 5-8-5 ring systems are widely occurring in nature but their syntheses have been hampered by inherent ring strain and transannular interactions of the eight-membered ring system.  A novel strategy, which involves a [2+2]-photocycloaddition of highly functionalized cyclobutenes and cyclopentenones, followed by a thermolytic fragmentation of the resulting strained photoadducts was developed in our laboratory.  With this methodology, the desired 5-8-5 ring systems can be constructed in as few as six steps from commercially available materials.  Currently, the intramolecularSean McCarthy modification of the methodology is being applied to the total synthesis of a diterpenoid natural product, cycloaraneosene.




5-8-5 Ring System

“Intramolecular [2+2]-Photocycloaddition/Thermal Fragmentation Approach toward 5-8-5 Ring Systems” Priscilla C.-K. Lo, Marc L. Snapper Org. Lett. 2001, 3, 2819-2821.
“[2+2]-Photocycloaddition/Thermal Retrocycloaddition.  A New Entry into Functionalized 5-8-5 Ring Systems” Michele L. Randall, Priscilla C.-K. Lo, Peter J. Bonitatebus, Jr., Marc L. Snapper J. Am. Chem. Soc. 1999, 121, 4534-4535.

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