Oxidopyrylium-Alkene [5 + 2] Cycloaddition Conjugate Addition Cascade (C³) Sequences: Scope, Limitation, and...

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Reaction Methodology

Background:

• Cycloaddition reactions are fundamental in organic synthesis for constructing cyclic molecules.
• Oxidopyrylium-alkene cycloadditions offer a unique pathway to complex ring systems.
• Cascade reactions, combining multiple transformations in one pot, enhance synthetic efficiency.

Purpose of the Study:

• To develop and investigate novel oxidopyrylium-alkene [5 + 2] cycloaddition conjugate addition cascade (C3) sequences.
• To explore the scope and limitations of intramolecular C3 reactions involving terminal alkenes, enals, and enones.
• To synthesize five- and six-membered carbocycles and heterocycles using this cascade methodology.

Main Methods:

• Investigated intramolecular cycloadditions using substrates with varying tether lengths.
• Employed terminal alkenes, enals, and enones as reaction partners.
• Utilized a combination of experimental studies and theoretical calculations to elucidate the reaction mechanism.

Main Results:

• Successfully demonstrated the oxidopyrylium-alkene [5 + 2] cycloaddition conjugate addition cascade (C3) sequences.
• Synthesized diverse five- and six-membered carbocycles and heterocycles.
• Established the scope and limitations of the C3 cascade for intramolecular cyclizations.

Conclusions:

• The developed C3 sequences provide an efficient route to carbocyclic and heterocyclic compounds.
• The study clarifies the mechanistic pathway through experimental and computational evidence.
• This methodology expands the toolkit for constructing complex cyclic structures in organic synthesis.