Asymmetric Diels‐Alder Reaction Catalyzed by Facile Recoverable Ionically Core‐Corona Polymer Microsphere‐Immobilized MacMillan Catalyst

Abstract

AbstractCore‐corona polymer microsphere having sulfonic acid moiety was successfully synthesized by the surface initiated‐atom transfer radical polymerization (SI‐ATRP) of an achiral monomer with phenyl p‐styrenesulfonate using benzyl halide‐functionalized polymer microsphere, followed by the regeneration of sulfonic acid. Ionically core‐corona polymer microsphere‐immobilized MacMillan catalyst was successfully synthesized by the neutralization reaction between core‐corona polymer microsphere having sulfonic acid moiety and chiral imidazolidinone precursor. The catalyst containing hydrophobic core and corona exhibited high catalytic activity with excellent enantioselectivity (99% ee for the exo isomer and >99% for the endo isomer) in the asymmetric Diels‐Alder reaction of trans‐cinnamaldehyde and 1,3‐cyclopentadiene. The catalyst with more than 1μm diameter could be recovered quantitatively by centrifugation and reused at least four cycles without loss of the enantioselectivity.