Jacobsen or “Jacobsen’s catalyst” is the common name for N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III), a heterocycle used in a multitude of chemical syntheses and catalytic reactions. The substance is a coordination compound produced from manganese and salen-type ligands. Jacobsen is most renowned for its use as an asymmetric catalyst in Jacobsen epoxidations, a reaction which induces prochiral alkenes transformation into epoxides.
The structure of this ligand is modifiable for a wide range of reaction uses. Coordinated with olefins, Jacobsen can function in asymmetric epoxidation or as a catalytic reagent of enantioselective epoxidation. It is employed in asymmetric α-hydroxylation of silyl enol ethers. Jacobsen is also involved in the synthesis of phenylisoserine, the Taxol side chain and cis-1-amino-2-indanol.
The theorized mechanism of Jacobsen is based on its ability to epoxidize conjugated alkenes. It’s believed Jacobsen is associated with radical intermediates that are stabilized by the substrate’s conjugated nature. Non-conjugated alkenes are less likely to display substrate-stabilized radicals, leading to a lower possibility for radical intermediate. Jacobsen’s ability to selectively epoxidize cis-alkenes is more difficult with terminal and trans-alkenes unless it is structurally altered.
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