Synthesis and catalytic properties of p-acylthio(phenylacetylene)(n) substituted chiral manganese salen complexes

The syntheses of three new salen ligands that are tethered to a p-acylthio( phenylacetylene),, linker are described. The two key steps in the syntheses are coupling of the p-acylthio(phenylacetylene),, linker (n=0-2) with a 5- iodosalicylaldehyde and the subsequent condensation of the aldehyde moiety of the formed adducts with the monoimine of (S,S)-1,2-diphenylethylenediami ne to give the salen ligands. In the catalytic asymmetric epoxidation react ions of (Z)-2-methylstyrene, performed using the Mn-salen complexes of thes e new ligands, high diastereo selectivities of up to 20:1 and enantioselect ivities of up to 89% ee are obtained. The results are compared with the ana logous reaction using Jacobsen's asymmetric epoxidation catalyst and the re sults are very similar. The synthesised ligands are promising candidates fo r the immobilisation of chiral Mn-salen complexes on gold electrodes and su rfaces.