Triple-Dearomative Photocycloaddition: A Strategy to Construct Caged Molecular Frameworks

Abstract

An unprecedented caged 2H-benzo-dioxo-pentacycloundecane framework was serendipitously obtained in a single transformation via triple-dearomative photocycloaddition of chromone esters with furans. This caged structure was generated as part of an effort to access a tricyclic, oxygen-bridged intermediate enroute to the dihydroxanthone natural product nidulalin A. Reaction scope and limitations were thoroughly investigated, revealing the ability to access a multitude of synthetically challenging caged scaffolds in a two-step sequence. Photophysical studies provided key mechanistic insights on the process for formation of the novel caged scaffold.

Photochemical dearomative skeletal modifications of heteroaromatics

“…Intermolecular photocycloaddition of single five membered-heteroarenes (furan, pyrrole) is synthetically challenging considering their high triplet energy. Recently, Porco and coworkers serendipitously achieved triple-dearomative photocycloaddition of furans and pyrroles for creating an intriguing caged molecular framework ( Scheme 36 ), 115 which has potential applications in drug discovery and medicinal chemistry. Regarding the mechanism, the UV light (370 nm) can excite chromone 352, generating triple excited state 352*.…”