Bifunctional catalysts stabilized on nanocrystalline magnesium oxide for one-pot synthesis of chiral diols

Abstract

New bifunctional catalysts composed of PdCl₄^2-, OsO₄^2- and OsO₄^2-, WO₄^2- designed and prepared by a counterionic stabilization technique involving the reactions of Na₂PdCl₄-K₂OsO₄ and K₂OsO₄-Na₂WO₄ with nanocrystalline MgO are well characterized. These bifunctional catalysts, NAP-Mg-PdOs and NAP-Mg-OsW perform tandem Heck asymmetric dihydroxylation and asymmetric dihydroxylation-N-oxidation reactions, respectively, in the presence of the chiral ligand 1,4-bis(9-o-dihydroquinidinyl)phthalazine [(DHQD)₂PHAL] in a single pot. It is quite impressive to note that H₂O₂ is used as a terminal oxidant to provide N-methylmorpholine N-oxide (NMO) in situ by the oxidation of N-methylmorpholine (NMM) in the asymmetric dihydroxylation-N-oxidation catalyzed by NAP-Mg-OsW.