Reusable chiral bis(oxazoline)–copper complexes immobilized by donor–acceptor interactions on insoluble organic supports

Heterogeneous asymmetric Diels–Alder reactions between cyclopentadiene and 3-but-2-enoyl-oxazolidin-2-one were efficiently promoted by reusable chiral bis(oxazoline)–copper catalysts, immobilized through charge transfer interactions with trinitrofluorenone, that was covalently grafted on Merrifield resins. The modified support was also used for the synthesis of both enantiomers of the target product, thanks to the non-covalent anchoring of the catalyst that allowed its easy removal and exchange.