Synthesis of chiral half-sandwich rhodium oxazoline complexes and their use as asymmetric Diels–Alder catalysts

Abstract

The reaction of [(η-C₅Me₅)RhCl₂]₂ with bidentate oxazoline containing ligands provides the cations [(η-C₅Me₅)RhClL]⁺ 1–3, of which {1, L = 2,2′-isopropylidenebis[4-isopropyl-2-oxazoline] and 3, L = 4-isopropyl-2-(2-pyridyl)-1,3-oxazoline} are structurally characterised by X-ray diffraction; treatment of these with AgSbF₆ gives dications which are enantioselective catalysts for the asymmetric Diels–Alder reaction between methacrolein and cyclopentadiene.