Molybdenum acetylacetonate complexes epoxides

Epoxides undergo deoxygenation upon treatment with vanadium or molybdenum acetylacetonate complexes, although their stereoselectivity is low. When the molybdenum(VI) oxo complex MoO(S2CNEt2)2 is employed, the deoxygenation proceeds with retention of configuration. For example, cw-2-butene oxide is converted to c -2-butene at 130 C in 83% yield. ... 

The chiral ligand (44) was prepared starting from the cyclic a-amino acid (S)-proline80). Recently, similar chiral catalysts and related molybdenum complexes involving optically active N-alkyl-P-aminoalcohols as stable chiral ligands and acetylacetone as a replaceable bidentate ligand, were designed for the epoxidation of allylic alcohols with alkyl hydroperoxides which could be catalyzed by such metal complexes 8,). 

The first reaction (346) consists of hydroperoxide formation by a typical autoxidation process, and the second represents selective epoxidation by the hydroperoxide. In the absence of the autoxidation catalyst, no reaction is observed under these conditions due to efficient removal of chain-initiating hydroperoxide molecules by reaction (347). Optimum selectivities obtain when the autoxidation catalyst is of low activity, which implies a low total activity of the catalytic system. The molybdenum complexes related to Mo02(oxine)2 are among the most effective catalysts for epoxidation.496 Although the autoxidation catalysts were limited to two types (phosphine complexes of noble metals and transition metal acetylacetonates), there is no reason, a priori, why other complexes such as naphthenates should not produce similar results. 

Among the most active transition metals are Mo and V, and both are effective in their highest oxidation state during reaction. Linden and Farona have foimd that Mo(V) is inactive for the epoxidation reaction and that V(IV) is converted to V (V) when contacted with a hydroperoxide [467]. The metals are added as compounds soluble in the reaction mixture, for example, Mo(CO)6, MoO2(acac), and VO(acac)2 (acac = monoanion of acetylacetone). Sheldon and Van Doom [266] have found that irrespective of the starting material, all molybdenum catalysts give rise to a common compound, a 1,2-diol complex (Fig. 1.11b). This is formed... 

The polyitnide bead bearing a triazole residue was used to immobilize a stable and active Mo(VI) epoxidation catalyst. The polyimide was refluxed with molybdenyl acetylacetonate in ethanol for 3days. Upon completion, a polyimide-Mo complex catalyst was filtered and extracted with ethanol in a Soxhiet apparatus for 3 days. The supported complex was dried thoroughly under vacuum. The molybdenum content was measured by inductively coupled plasma (ICP) to be l.OSmmolg for PI-DAT.Mo and l. lOmmolg for CPI-DAT.Mo. 

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