Asymmetric epoxidation of alkenes with aqueous t-BuOOH catalyzed by novel chiral complexes of chromium(III) containing tridentate Schiff-base ligands

The [CrIII(α-TDL1*)(bipy)(Cl)] (1) and [CrIII(TDL2*)(bipy)(Cl)] (2) complexes (where H2TDL1* = N-3,5-di-(t-butyl)salicylidine-d-glucosamine, H2TDL2* = N-3,5-di-(tertiarybutyl)salicylidine-l-alanine, bipy = bipyridyl) have been synthesized and characterized by analytical, spectral (UV–vis and IR), molar conductivity, magnetic moment and electrochemical studies. Complexes 1 and 2 catalyzed the epoxidation of styrenes, stilbenes, 1-methylcyclohexene and 1,2-dihydronapthalene using aqueous tert-butyl hydroperoxide (t-BuOOH) as terminal oxidant. The selected alkenes were converted to their corresponding epoxides exhibiting moderate enantioselectivity at ambient temperature.

Graphical abstractMixed-ligand chromium catalyst containing tridentate sugar-based chiral ligand and bipyridine effect asymmetric induction in epoxidation of styrene using aqueous t-BuOOH as a terminal oxidant. Figure optionsDownload full-size imageDownload as PowerPoint slide