Sodium hypochlorite, olefin epoxidation

F. Montanari, M. Penso, S. Quici, P. Vigano, Highly efficient sodium hypochlorite olefin epoxidations catalyzed by imidazole or pyridine "tailed" manganese porphyrins under two-phase conditions. Influence of pH and of the anchored ligand, /. Org. Chem. 50 (1985) 4888. 

Metallosalen complex [salen = N, A-ethylenebis(salicyldeneaminato)] has a structure similar to metalloporphyrin, and these two complexes catalyze the epoxidation of olefins. For example, Kochi et al. have found that metallosalen complexes such as (salen )manganese(III) [25] and (salen)chromium(IIl) complexes [26] (hereafter referred to as Mn- and Cr-salen complexes, respectively) serve as catalysts for the epoxidation of unfunctionalized olefins by using iodosylbenzene [25] or sodium hypochlorite [27], In particular, cationic Mn-salen complex is a good catalyst for epoxidation of unfunctionalized olefins, which proceeds through an oxo(salen)manganese(V) species (Scheme 6B.14) [25,28], The presence of oxo-Mn(V)-salen... 

These catalysts, 11-13, show good enantioselectivity ranging from 80 to 95% ee in the epoxidation of conjugated cfs-di- and tri-substituted olefins. Epoxidation of "good substrates such as 2,2-dimethylchromene derivatives proceeds with excellent enantioselectivity (>95% ee). Since the results obtained with these first-generation Mn-salen catalysts have been reviewed [21,33], only typical examples are shown in Table 6B.1. These reactions are usually carried out in the presence of donor ligand [34] such as 4-phenylpyridine A -oxide with terminal oxidants such as iodosylbenzene and sodium hypochlorite as described above. However, the use of some other terminal oxidants under well-optimized conditions expands the scope of the Mn-salen-... 

Oxidation of internal perfluoroolefins by alkaline solutions of hydrogen peroxide and alkaline and alkaline-earth hypohalides leads to the formation of olefin oxides, the yield of the target product being 40-50%. The reaction with sodium hypochlorite in an alkali in the presence of acetonitrile is an example of epoxidation performed by the nucleophilic attack of the OC1-anion of the multiple bond with further elimination of the chloride anion by the intermediate carbanion (79IZY2509, 79IZV2812, 79RP666176,... 

The asymmetric oxidation of indene to the corresponding epoxide (Equation 24) is carried out commercially by Sepracor on a small scale. Chiral indene oxide is an intermediate in the synthesis of crixivan (an HIV protease inhibitor). Reaction is carried out at 5°C with moderately high turnover numbers in the presence of an exotic donor ligand ( P3NO , 3-phenylpropylpyridine N oxide) and sodium hypochlorite as the terminal oxidant. A similar epoxidation of a simple cis olefin (Equation 25) leads to an enantiomerically pure amino-alcohol used in the synthesis of taxol, a potent anticancer drug. 

The epoxidation of simple olefins which cannot benefit from secondary interactions brings some formidable problems that were solved by sophisticated catalyst design, mainly by the groups of Jacobsen and Katsuki in the 1990 s. A class of square planar salen complexes was chosen (Figure 19, for example) capable of giving a metal-oxo derivative by reaction with monooxygen donors such as iodosobenzene or sodium hypochlorite (the preferred oxidant). A series... 

As examples, the use of sodium hypochlorite in a biphasic system in the presence of phase-transfer catalysts, a high-yielding epoxidation of a variety of electron-deficient trisubstituted and /ra j--disubstituted olefins with excellent enantioselectivity, can take place (Scheme 27) <2004JA6844>. 

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. 

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. 

H. Amatsu, T. K. Miyamoto, Y. Sasaki, Olefin epoxidation catalyzed by sterically bulky metallo-porphyrins (Metal=Fe,Mn) by use of sodium-hypochlorite as an oxygen source-a kinetic-study. Bull. Chem. Soc. pn. 61 (1988) 3193. 

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 ... 

---