Ring-Opening Cyclization of Spirocyclopropanes Using Sulfoxonium Ylides

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Heterocyclic Chemistry

Background:

• Cyclopropane ring-opening reactions offer versatile synthetic pathways.
• Spirocyclopropane systems present unique structural motifs for chemical transformations.
• Fused heterocyclic compounds are prevalent in natural products and pharmaceuticals.

Purpose of the Study:

• To investigate the regioselective ring-opening cyclization of cyclohexane-1,3-dione-2-spirocyclopropanes.
• To explore the synthesis of fused pyranone ring systems using sulfoxonium ylides.
• To evaluate the scope and limitations of this novel synthetic methodology.

Main Methods:

• Reaction of cyclohexane-, cycloheptane-, and cyclopentane-1,3-dione-2-spirocyclopropanes with dimethylsulfoxonium methylide.
• Utilizing various sulfoxonium ylides (ethylide, butylide, benzylide) to explore substituent effects.
• Characterization of the resulting fused ring systems and their derivatives.

Main Results:

• Regioselective formation of 2,3,4,6,7,8-hexahydro-5H-1-benzopyran-5-ones in good to high yields.
• Successful construction of [7.6]- and [5.6]-fused ring systems from cycloheptane and cyclopentane precursors.
• Formation of 2,3-trans-disubstituted products with different sulfoxonium ylides, indicating the dimethyl group acts as a dummy substituent.
• Efficient conversion of 2- and 3-phenylhexahydrobenzopyran-5-ones into 5-hydroxyflavan and 5-hydroxyisoflavan.

Conclusions:

• The developed method provides an efficient route to substituted hexahydrobenzopyranones.
• The reaction demonstrates broad applicability to different ring sizes and sulfoxonium ylides.
• The synthesized compounds serve as valuable precursors for flavan and isoflavan derivatives, expanding synthetic possibilities in heterocyclic chemistry.