Manganese complexes olefin epoxidation

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 ... 

By complexation of MnNaY with 1,4,7-trimethyltriazacyclononane, a new heterogeneous catalyst was obtained for olefin epoxidation with H202. Excellent epoxide selectivities were obtained, with limited epoxide solvolysis. The oxygenation appears to go through a radical intermediate. The manganese trizacyclononane epoxidation catalyst was also heterogenized via surface gly-cidylation.103... 

SCHEME 33. Asymmetric epoxidation of olefins catalyzed by salen manganese complexes. 

Catalytic, asymmetric epoxidations are one of the most important asymmetric processes. In 1980 Katsuki and Sharpless reported a stoichiometric asymmetric epoxidation of allylic alcohols, a method that was later improved to become a catalytic process.9 Moreover, catalytic asymmetric epoxidations of unfunctionalized olefins using salen-manganese complexes have been reported independently by several groups.10-12 In striking contrast to these successful achievements, an efficient catalytic asymmetric epoxidation of enones with broad generality has not been developed.13-22... 

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. 

Zhang, W., Loebadi, J.L., Wilson, S.R. and Jacobsen, E.N. (1990) Enantioselective epoxidation of unfimctionalized olefins catalyzed by (salen)manganese complexes. Journal of the American Chemical Society, 112, 2801-2803. 

A. Murphy, G. Dubois, T. D. P. Stack, Efficient epoxidation of electron-deficient olefins with a cationic manganese complex, J. Am. Chem. Soc. 125 (2003) 5250. 

W. Zhang, E. N. Jacobsen, Asymmetric olefin epoxidation with sodium hypochlorite catalyzed by easily prepared chiral manganese(III) salen complexes, /. Org. Chem. 56 (1991) 2296. 

G. Yin, A. M. Danby, D. Kitko, J. D. Carter, W. M. Scheper, D. H. Busch, Olefin epoxidation by alkyl hydroperoxide with a novel cross-bridged cyclam manganese complex Demonstration of oxygenation by two distinct reactive intermediates. [Erratum to document cited in CA146 316400], Inorg. Chem. 46 (2007) 2173. 

B. Meunier, E. Guilmet, M. De Carvalho, R. Poilblanc, Sodium hypochlorite A convenient oxygen source for olefin epoxidation catalyzed by (porphyrinato)manganese complexes, ]. Am. Chem. Soc. 106 (1984) 6668. 

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