Study of Diels–Alder Reactions of Purpurogallin Tetraacetate with Various Dienophiles

Abstract

Purpurogallin or (6E,8Z)-2,3,4,6-tetrahydroxy-5H-benzo[7]annulen-5-one is a benzotropolone possessing a dienic system and known to inhibit the TLR1/TLR2 activation pathway. We have recently described the easy green synthesis of purpurogallin from pyrogallol catalyzed by a copper complex or by vegetable oxidases. The purpurogallin was acetylated and the tetra-acetate derivative thus obtained was engaged in a Diels–Alder reaction with various dienophiles (benzoquinone, maleic anhydride, ethylmaleimide, phenylmaleimide, etc.). The results obtained are presented and discussed.

Keywords

• purpurogallin
• purpurogallin tetraacetate
• [4+2] cycloaddition
• dienophiles
• density functional theory (DFT)