Multicomponent Green Synthesis Involving Aryl Aldehydes and Trapped Enols: Dimerization over Cyclization

Area of Science:

• Organic Synthesis
• Green Chemistry
• Medicinal Chemistry

Background:

• Literature contains mischaracterized products from multicomponent synthesis involving aryl aldehydes and trapped enols (4-hydroxycoumarin or 4-hydroxy-6-methyl-2-pyrone).
• Many reported cyclization products are, in fact, dimers, necessitating correction and re-characterization.

Purpose of the Study:

• To correct the scientific literature regarding multicomponent synthesis products.
• To fully characterize the dimerization products, bis-coumarins and bis-pyrones.
• To develop a green, efficient synthetic method for these dimers.

Main Methods:

• A one-pot reaction in water was employed, avoiding hazardous organic solvents.
• A catalytic amount of acid was used, simplifying purification without chromatography.
• The synthesis adhered to strong green chemistry principles.

Main Results:

• High yields (24-96%) of bis-coumarins and bis-pyrones were successfully synthesized.
• The first report of a meta-substituted bis-pyrone (4i) was achieved.
• Characterization and photophysical properties of the synthesized dimers were determined.

Conclusions:

• A novel green synthetic route for bis-coumarins and bis-pyrones was established.
• The synthesized dimers show potential as acetylcholinesterase (AChE) inhibitors for anti-Alzheimer's therapy.