Manganese bleaching catalyst

Ordinary alkenes (without an allylic OH group) have been enantioselectively epoxidized with sodium hypochlorite (commercial bleach) and an optically active manganese-complex catalyst. Variations of this oxidation use a manganese-salen complex with various oxidizing agents, in what is called the Jacobsen-Katsuki... 

The applicability of the Sharpless asymmetric epoxidation is however limited to functionalized alcohols, i.e. allylic alcohols (see Table 4.11). The best method for non-functionalized olefins is the Jacobsen-Kaksuki method. Only a few years after the key publication of Kochi and coworkers on salen-manganese complexes as catalysts for epoxidations, Jacobsen and Kaksuki independently described, in 1990, the use of chiral salen manganese (111) catalysts for the synthesis of optically active epoxides [276, 277] (Fig. 4.99). Epoxidations can be carried out using commercial bleach (NaOCl) or iodosylbenzene as terminal oxidants and as little as 0.5 mol% of catalyst. The active oxidant is an oxomanganese(V) species. 

Wieprecht, T., Heinz, U., Xia, J. et al., Terpyridine-Manganese Complexes A new class of bleach catalysts for detergent applications, J. Surfactant Detergents, 7 59-66, 2004. 

Park, H. W., Lee, S. Y., Ahn., J. B. et al., Synthesis of novel bleaching catalyst containing macrocy-clic manganese complexes and potential applications in laundry detergents, J. Surfactant Detergents, 9 385-389, 2006. 

Fueled by the success of the Mn (salen) catalysts, new forays have been launched into the realm of hybrid catalyst systems. For example, the Mn-picolinamide-salicylidene complexes (i.e., 13) represent novel oxidation-resistant catalysts which exhibit higher turnover rates than the corresponding Jacobsen-type catalysts. These hybrids are particularly well-suited to the low-cost-but relatively aggressive-oxidant systems, such as bleach. In fact, the epoxidation of trans-P-methylstyrene (14) in the presence of 5 mol% of catalyst 13 and an excess of sodium hypochlorite proceeds with an ee of 53%. Understanding of the mechanistic aspects of these catalysts is complicated by their lack of C2 symmetry. For example, it is not yet clear whether the 5-membered or 6-membered metallocycle plays the decisive role in enantioselectivity however, in any event, the active form is believed to be a manganese 0x0 complex <96TL2725>. 

Hage R, Iburg JE, Kerschner J, Koek HH, Lempers E, Martens RJ, Racheria US, Russe WW, Suarthoff T, Vliet M, Warner JB, Wolf L, Krijnen B. Effect of manganese catalysts for low-temperature bleaching. Nature 1994 369 637-639. 

PLEX HT also has the ability to chelate copper and manganese in most forms other than as the metal during the caustic saturation step and subsequent rinsing. Copper and manganese are powerful peroxide decomposition catalysts. They must be eliminated as much as possible prior to the peroxide bleaching step. 

Recently, a granulated manganese (Ill)-saltren complex [35] has been incorporated in bleach boosters and a powder detergent in Europe. Activated by peroxide, the catalyst has a bleaching optimum around pH 11, and is most effective between 30 and 60°C. It bleaches on fabric but also fugitive dyes in solution and prevents graying of white fabrics. It is gentle to fabrics and fibers and compatible with a number of enzymes [36]. 

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