A Tandem Iridium-Catalyzed "Chain-Walking"/Cope Rearrangement Sequence

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Tandem reactions offer efficient pathways to complex molecules.
• Iridium catalysis enables unique transformations in organic synthesis.
• Cyclopropane derivatives are versatile synthetic intermediates.

Purpose of the Study:

• To develop a novel iridium-catalyzed tandem olefin migration/Cope rearrangement.
• To synthesize complex annulenes and bicyclic cycloheptenones.
• To explore the scope and limitations of the new methodology.

Main Methods:

• Iridium-catalyzed tandem reaction of alkenyl ω-ene cyclopropanes.
• Utilizing cyclopropyl esters derived from 1,ω-dienes and alkenyldiazo compounds.
• Employing Kulinkovich reaction for bicyclic cycloheptenone synthesis.

Main Results:

• Successful synthesis of complex annulenes as single diastereomers.
• Achieved long-range olefin migration (up to 10 positions) coupled with Cope rearrangement.
• Demonstrated tolerance of various functional groups, yielding densely functionalized products.
• Extended methodology to produce bicyclic cycloheptenones from alkenyl cyclopropanols.

Conclusions:

• The reported iridium-catalyzed tandem reaction is a powerful tool for constructing complex molecular architectures.
• This methodology provides efficient access to valuable annulene and cycloheptenone scaffolds.
• The reaction's functional group tolerance and broad applicability highlight its synthetic utility.