A new xanthone synthesis from the Diels–Alder reaction between 2-vinylchromen-4-ones and cyclopentanone enamine

Abstract

The reaction between 2-vinylchromen-4-ones and 1-pyrrolidinylcyclopentene give substituted 2,3,3a,4-tetrahydrocyclopenta[a]xanthen-11(5H)-ones; the stereochemistry of the product shows that the initial step in the reaction may be considered to be an exo-addition Diels–Alder with inverse electron demand.