Jacobsen’s Catalyst

Abstract

Enantioselective epoxidation of olefins is a challenging and useful synthetic transformation. [1] Since its introduction in the early nineties, Jacobsen’s catalyst has proved reliable for highly enantioselective epoxidation of prochiral olefins. [2] Belonging to the salen-ligand class, [3] the catalyst has a manganese core in a square planar geo­metry, stabilised with a chlorine atom in the axial position. [2] Several stoichiometric oxidants have been used successfully, [4] with NaOCl the most frequently involved. [1a] [b] [5] Easy to prepare, the catalyst has become commercially available in both enantiomeric forms. [6] Applied also for the enantioselective oxidation of sulfides to sulf­oxides, [4e] and for the oxidation of hydrocarbons at the benzylic position, [4c] the catalyst has even been synthesised in a dimeric form for the epoxidation of olefins under heterogeneous conditions. [7] Recently, it has provided the first example of didehydrogenation of secondary hydroxyl­amines to the corresponding nitrones. [8]