Manganese complexes amine oxides

Jacobsen and co-workers have devised highly enan-tiospecific manganese complexes for epoxidations of olefins with sodium hypochlorite.94 Peracids and amine N-oxides can also be used as oxidants. A typical catalyst is shown in 10.43 ... 

Manganese(tl) complexes,, 3, 9-82 acctylacetonates, 48 acetylides, 14 alcohols, 37 alkoxides, 37 alkyl phosphines, 13 alkyls, 12 amides, 15, 16 amine oxides, 39 amines, 16 amino acids, 43, 62 sulfur containing, 70 ammines, 15 antimony ligands, 31-34 arsenates, 4,5, 46 arsenic ligands, 31-34 arsenic oxides, 39 aryls, 12, 14 azides, 22 binary alkyls, 13 bipyridyl, 24, 25 anions, 25... 

Sheng and Zajacek [182] have shown that vanadium complexes are somewhat superior catalysts to molybdenum. Both give good selectivity to amine oxide but reaction rates are faster when vanadium complexes are used. Compounds of tungsten, niobium and tantalum were poorer catalysts whereas chromium, cobalt, manganese and iron complexes were ineffective. 

Photooxidation of the metal center is not a commonly observed reaction with metalloporphyrins, but examples do exist. Both chromium(III) and manganese(III) porphyrins will undergo photooxidation reactions under appropriate conditions. Perchlorate amine-, oxides, and methyl viologen (MV " ) have been used as oxidants in these photoreactions, and photolysis of the corresponding azido complexes results in the formation of a nitrido complex where the metal ion has undergone a two-electron oxidation. Examples of such reactions are ... 

Another situation is observed when salts or transition metal complexes are added to an alcohol (primary or secondary) or alkylamine subjected to oxidation in this case, a prolonged retardation of the initiated oxidation occurs, owing to repeated chain termination. This was discovered for the first time in the study of cyclohexanol oxidation in the presence of copper salt [49]. Copper and manganese ions also exert an inhibiting effect on the initiated oxidation of 1,2-cyclohexadiene [12], aliphatic amines [19], and 1,2-disubstituted ethenes [13]. This is accounted for, first, by the dual redox nature of the peroxyl radicals H02, >C(0H)02 and >C(NHR)02 , and, second, for the ability of ions and complexes of transition metals to accept and release an electron when they are in an higher- and lower-valence state. 

It is quite often possible to prepare hydroxypyridinone complexes directly by one-pot synthesis from the appropriate hydroxypyranone, amine, and metal salt 90-92). They can also be prepared by reacting complexes such as P-diketonates with hydroxypyridinones (see e.g., Ce, Mo later). Several maltolate complexes, of stoichiometry ML2, ML3, ML4, or MOL2, have been prepared by electrochemical oxidation of the appropriate metal anode, M — a first-row d-block metal (Ti, V, Cr, Mn, Fe, Co, Ni), In, Zr, or Hf, in a solution of maltol in organic solvent mixtures 92). Preparations of, e.g., manganese(III), vanadium(III), or vanadium(V) complexes generally involve oxidation... 

Without additives, radical formation is the main reaction in the manganese-catalyzed oxidation of alkenes and epoxide yields are poor. The heterolytic peroxide-bond-cleavage and therefore epoxide formation can be favored by using nitrogen heterocycles as cocatalysts (imidazoles, pyridines , tertiary amine Af-oxides ) acting as bases or as axial ligands on the metal catalyst. With the Mn-salen complex Mn-[AI,AI -ethylenebis(5,5 -dinitrosalicylideneaminato)], and in the presence of imidazole as cocatalyst and TBHP as oxidant, various alkenes could be epoxidized with yields between 6% and 90% (in some cases ionol was employed as additive), whereby the yields based on the amount of TBHP consumed were low (10-15%). Sterically hindered additives like 2,6-di-f-butylpyridine did not promote the epoxidation. 

The electrochemical oxidation of tyramine in NaOH/MeOH media gives films of polytyramine (25). The film, on a platinum electrode, can complex copper(II) ions from aqueous media and cobalt(II), iron(II), manganese(II) and zinc(II) from organic media. X-ray photoelectron spectroscopy established that coordination of the metal ions had occurred. For cobalt, evidence of coordination to both ether and amine functions is obtained, but for the other metal ions evidence of ether coordination is less definitive. 

The cerium(IV) oxidation of lactyllactic acid49 and of 4-oxopentanoic acid50 in aqueous nitric acid solutions shows first-order dependence of the reaction on both cerium(IV) and substrate. A 1 1 complex formation between manganese(III) and amine, which later decomposes in the rate-limiting step, best explains the kinetics of oxidation of aliphatic amines by cerium(IV) in nitric acid medium in the presence of manganese(II).51 The kinetics of oxidation of naphthalene, 2-methyhiaphthalene, and a-naphthol with cerium(IV) in perchloric acid solutions have been studied.52 Use of a 50-fold molar excess of cerium(IV) perchlorate results in complete oxidation of fluorophenols to CO2, HCO2H, and HF in 48 h at 50 °C.53... 

Asymmetric imidations of aryl alkyl sulfides with [(tosylimino)iodo]ben-zene, catalyzed by various chiral (salen)manganese(III) complexes, have been investigated in some detail [31,32]. The influence of catalyst structure, solvent, temperature, 3°-amine AT-oxides, and the presence of molecular sieves on product yields and the enantioselectivity of imidation with 17 was evaluated. Enan-tioselectivities as high as 90 % ee and 97 % ee with methyl 2-nitrophenyl sulfide and methyl 2,4-dinitrophenyl sulfide, respectively, were achieved. 

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