Study of the Diels-Alder reactions of purpurogallin tetraacetate with various dienophiles

Purpurogallin (1,7,8,9-tetrahydroxy-2H-benzo[7]annulen-2-one) is a benzotropolone displaying a dienic system and known to inhibit TLR1/TLR2 activation pathway system. We have recently described the easy green synthesis of purpurogallin from pyrogallol catalyzed by a copper complex or by vegetable oxidases. Moreover, Purpurogallin was acetylated and the tetraacetate obtained can be converted with various dienophiles (benzoquinone, maleic anhydride, ethylmaleimide, azodicarboxylate…) in Diels-Alder products. The results obtained will be presented and discussed. Theoretical calculations using the conceptual DFT have been performed.