Abstract: The present invention provides a process for the epoxidation of alkenes of the formula (1) where R1, R2, R3 and R4 are, independently of one another, hydrogen, C1-C20-alkyl, C1-C12-alkoxy, C6-C10-aryl, —CHOH—CH3, —CH—NH2—CH3 or carboxy, using air or oxygen over a catalyst comprising compounds of the formula (2) MoxOy(L)z  (2) where x is 1, 2 or 3, y is an integer from 0 to 2x+1, z is an integer from 1 to 2x, where the ligand L is a compound of the formula (3) or (4) where X is a nitrogen, oxygen or sulfur atom, Y is hydrogen, C1-C8-alkyl, C1-C8-alkoxy, F, Cl, Br, I, COOCH3, C6-C14-aryl or C3-C8-cycloalkyl, R7 and R8 form a ring containing from 4 to 8 carbon atoms onto which one or two aromatic rings may be fused, R5 and R6 are hydrogen, branched or straight-chain C1-C12-alkyl or branched or straight-chain C1-C12-haloalkyl which are substituents on the ring formed by R7 and R8 and/or the rings fused onto this ring, or t

Abstract: A catalyst for the selective oxidation of olefins in the presence of air or oxygen, comprising a compound of the formula (1) MoxOy(L)z  (1) where x is 1, 2 or 3, y is an integer from 0 to 2x+1, z is an integer from 1 to 2x, wherein the ligand L is a compound of the formula (2) or (3)  where n is 0 or 1, X is a nitrogen, oxygen or sulfur atom, Y is hydrogen, C1-C8-alkyl, C1-C8-alkoxy, F, Cl, Br, I, COOCH3, C6-C14-aryl or C3-C8-cycloalkyl, R3 and R4 form a ring containing from 4 to 8 carbon atoms onto which one or two aromatic rings may be fused, R1 and R2 are hydrogen, branched or straight-chain C1-C12-alkyl or branched or straight-chain C1-C12-haloalkyl which substitute the ring formed by R3 and R4 and/or the rings fused onto this ring, or the ligand L is a compound of the formula (4) or (5) where R is hydrogen, C1-C8-alkyl, C1-C8-alkoxy, COOCH3, carbonyl oxygen, C6-C14-aryl or C3-C8-cycloalkyl and n is 1 or 2 and m is from 1 to 6.

Abstract: Catalysts for the selective epoxidization of olefins with atmospheric oxygen, processes for their preparation and processes for the preparation of epoxides by oxidation of olefins with air or oxygen.Compounds of the formula (1) as catalysts for the selective epoxidization of alkenesM.sub.x O.sub.y (L).sub.z (1)in whichthe indices x, y and z have the following meaning:x is a whole number from 1 to 3, y is a whole number from 1 to 2x+1, y being selected so that the sum of x+z gives a metal oxidation number of +5 (vanadium) or +6 (molybdenum, ruthenium); z is a whole number in the range from 2 to 2x;M is molybdenum, ruthenium or vanadium andL is an N, 0 or S donor ligand.