Olefins with hydrogen peroxide

The observation that addition of imidazoles and carboxylic acids significantly improved the epoxidation reaction resulted in the development of Mn-porphyrin complexes containing these groups covalently linked to the porphyrin platform as attached pendant arms (11) [63]. When these catalysts were employed in the epoxidation of simple olefins with hydrogen peroxide, enhanced oxidation rates were obtained in combination with perfect product selectivity (Table 6.6, Entry 3). In contrast with epoxidations catalyzed by other metals, the Mn-porphyrin system yields products with scrambled stereochemistry the epoxidation of cis-stilbene with Mn(TPP)Cl (TPP = tetraphenylporphyrin) and iodosylbenzene, for example, generated cis- and trans-stilbene oxide in a ratio of 35 65. The low stereospecificity was improved by use of heterocyclic additives such as pyridines or imidazoles. The epoxidation system, with hydrogen peroxide as terminal oxidant, was reported to be stereospecific for ris-olefins, whereas trans-olefins are poor substrates with these catalysts. 

Clerid, M.G. and Ingallina, P. (1993) Epoxidation of lower olefins with hydrogen peroxide and titanium silicate. J. Catal., 140, 71-83. 

Therefore, the following mechanistic investigation of the epoxidation of olefins with hydrogen peroxide is constrained to reaction pathways which (1) involve HFIP in an sc or even sp conformation and (2) to hydrogen bonded HFIP aggregates comprising up to four alcohol monomers. 

Berkessel and Andreae reported that the catalytic activity of benzenearsonic acid in the epoxidation of olefins with hydrogen peroxide is potentiated in fluorinated alcohols such as Since Brpnsted acids do not effect epoxidation under these conditions, the... 

SCHEME 98. Arsonic acid-catalyzed epoxidation of olefins with hydrogen peroxide in ionic Mquids... 

Platinum(II) and ruthenium(II) complexes with chiral modified diphosphines like 47 or tetradentate P2N2 ligands like 48 have been used for the asymmetric epoxidation of olefins with hydrogen peroxide with ee values of 18-23%, which increased up to 41% when cationic solvato derivatives such as P2Pt(CF3)(CH2Cl2)(BF4) are used . Similar chiral inductions were reported for Ru derivatives, although the nature of the active intermediate was still in question. ... 

The efficiency of conjugated dehydrogenation of olefins with hydrogen peroxide was also confirmed in studies of propylene dehydrogenation to allene [60], The well-known process of propylene oxidative dehydrogenation to allene in the presence of iodine [61] at 625-700 °C gives low yields of the target product (3.6% allene) at low selectivity of the process (6%). 

The other main group elements which form peroxo complexes are d6 and d8 systems in group VIII including iridium, palladium and platinum. The ji-peroxo complexes do not generally catalyse the epoxidation of olefins with hydrogen peroxide,95,96 but it has been found that trifluoromethyl-substituted Pd(II) and Pt(II) hydroperoxides will perform such a transformation.97... 

Figure 3.32 Cleavage of olefins with hydrogen peroxide/ vanadium ( V) systems.

Heterogeneous systems have also been developed for the cleavage of olefins with hydrogen peroxide.174,175 Titanium-containing zeolites can be used to cleave olefins.176 Adam and co-workers have recently shown that acetophenone, an oxidation product from the Ti-zeolite catalysed oxidation of a-methyl-styrene, derives from 2-hydroxyperoxy-2-phenylpropan-l-ol as an intermediate (which they detected and isolated) (Figure 3.34).177... 

In this context it is interesting to note the recent reports of fluorous catalysis without fluorous solvents [68]. The thermomorphic fluorous phosphines, P[(CH2)m(CF2)7CF3]3 (m=2 or 3) exhibit ca. 600-fold increase in n-octane solubility between -20 and 80 °C. They catalyze the addition of alcohols to methyl propiolate in a monophasic system at 65 °C and can be recovered by precipitation on cooling (Fig. 7.20) [68]. Similarly, perfluoroheptadecan-9-one catalyzed the epoxidation of olefins with hydrogen peroxide in e.g. ethyl acetate as solvent [69]. The catalyst could be recovered by cooling the reaction mixture, which resulted in its precipitation. 

Box 3 Epoxidation of Higher Olefins with Hydrogen Peroxide... 

Epoxidation of olefins with hydrogen peroxide in the presence of Fe(acac)3 has been examined in the cases of stilbene, unsaturated alcohols, and fatty acids. From cis- and trans-olefins the main product is the trans isomer, formed via a biradical intermediate. Cholesterol undergoes /3-epoxidation. ... 

Peroxo Mo and W complexes catalyzed oxidation of alcohols and olefins with hydrogen peroxide to form oxiranes and lactones 03MI105. 

N. Mizuno, K. Yamaguchi, K. Kamata, Epoxidation of olefins with hydrogen peroxide catalyzed by polyoxometalates. Coord. Chem. Reu. 249 (2005) 1944. 

W. Adam, C. R. Saha-Moller, O. Weichold, NaY zeolite as host for the selective heterogeneous oxidation of silanes and olefins with hydrogen peroxide catalyzed by methyltrioxorhenium, J. Org. Chem. 65 (2000) 2897. 

A. Corma, P. Esteve, A. Martinez, S. Valencia, Oxidation of olefins with hydrogen peroxide and tert-butyl hydroperoxide on Ti-Beta catalyst, /. Catal. 152 (1995) 18. 

S. J. Yang, W. Nam, Water-soluble iron porphyrin complex-catalyzed epoxidation of olefins with hydrogen peroxide and fcrf-butyl hydroperoxide in aqueous solution, Inorg. Chem. ZT (1998) 606. 

Sharpless has shown that phenylselenic acid catalyzes the epoxidation of olefins with hydrogen peroxide or f-BuOOH [41]. However, the toxicity of selenium compounds precludes many applications of this catalytic epoxidation. To avoid contamination of the reaction products with selenium compounds polystyrene-bound phenylselenic acid has been used [42]. An alternative to the solid phase chemistry is the immobilisation of the selenium catalyst in the fluorous phase... 

Enantioselective Epoxidation of Olefins with Hydrogen Peroxide with CA[Mn]. 54... 

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