A Diels-Alder reaction of α-tropolone and electron-deficient dienophiles prompted by Et3N or silica gel was performed. Reaction with the highly reactive dienophile, N-methylmaleimide, proceeded smoothly in the presence of Et3N or silica gel to yield adducts as a mixture of endo and exo isomers. Both catalysts accelerated endo/exo isomerization of the product, and detailed examination of the reaction using hinokitiol and N-methylmaleimide revealed that isomerization proceeds via an intramolecular path without retro Diels-Alder reaction. Successful cycloaddition reactions were established with six other dienophiles: acrylonitrile, methyl acrylate, ethyl vinyl ketone, dimethyl fumalate, dimethyl malate, and dimethyl acetylenedicarboxylate, and the corresponding adducts were obtained in good to moderate yields.
All Science Journal Classification (ASJC) codes
- Drug Discovery
- Organic Chemistry