Epoxidation of alkenes by hydrogen peroxide catalysed by oxo(5,10,15,20-tetraphenylporphyiiinato)-molybdenum(V) complexes

Legemaat, G.; Drenth, W.; Schmidt, M.; Prescher, G.; Goor, G.

doi:10.1016/0304-5102(90)85207-x

Cited by 18 publications

(7 citation statements)

References 43 publications

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“…There are also several homogeneous coordination complexes that are active. These include porphyrins, − salens, − 1,4,7-triazacyclononane (tacn) derived catalysts, − and iron complexes from tetradentate diamine-dipyridine ligands. − Organic catalysts for epoxidation have also been developed, mainly for asymmetric transformations. , Some selenium, − arsenic, and organofluorine compounds are surprisingly active and selective catalysts, but they have obvious limitations with respect to large-scale “green” processes. However, the most pertinent category of epoxidation catalysts here are the “soluble metal oxides”.…”

Section: Introductionmentioning

confidence: 99%

“…9 There are also several homogeneous coordination complexes that are active. These include porphyrins, [10][11][12][13][14][15][16][17][18][19][20][21][22] salens, [23][24][25][26][27][28][29][30][31] 1,4,7-triazacyclononane (tacn) derived catalysts, [32][33][34][35][36][37][38][39][40][41] and iron complexes from tetradentate diamine-dipyridine ligands. [42][43][44] Organic catalysts for epoxidation have also been developed, mainly for asymmetric transformations.…”

Section: Introductionmentioning

confidence: 99%

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Manganese-Catalyzed Epoxidations of Alkenes in Bicarbonate Solutions

et al. 2002

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This paper describes a method, discovered and refined by parallel screening, for the epoxidation of alkenes. It uses hydrogen peroxide as the terminal oxidant, is promoted by catalytic amounts (1.0-0.1 mol %) of manganese(2+) salts, and must be performed using at least catalytic amounts of bicarbonate buffer. Peroxymonocarbonate, HCO(4)(-), forms in the reaction, but without manganese, minimal epoxidation activity is observed in the solvents used for this research, that is, DMF and (t)BuOH. More than 30 d-block and f-block transition metal salts were screened for epoxidation activity under similar conditions, but the best catalyst found was MnSO(4). EPR studies show that Mn(2+) is initially consumed in the catalytic reaction but is regenerated toward the end of the process when presumably the hydrogen peroxide is spent. A variety of aryl-substituted, cyclic, and trialkyl-substituted alkenes were epoxidized under these conditions using 10 equiv of hydrogen peroxide, but monoalkyl-alkenes were not. To improve the substrate scope, and to increase the efficiency of hydrogen peroxide consumption, 68 diverse compounds were screened to find additives that would enhance the rate of the epoxidation reaction relative to a competing disproportionation of hydrogen peroxide. Successful additives were 6 mol % sodium acetate in the (t)BuOH system and 4 mol % salicylic acid in the DMF system. These additives enhanced the rate of the desired epoxidation reaction by 2-3 times. Reactions performed in the presence of these additives require less hydrogen peroxide and shorter reaction times, and they enhance the yields obtained from less reactive alkene substrates. Possible mechanisms for the reaction are discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Manganese-Catalyzed Epoxidations of Alkenes in Bicarbonate Solutions

et al. 2002

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“…Inasmuch as molybdenum porphyrins can also catalyse epoxidation of alkenes with H 2 O 2 [8,9], we then examined the reaction between complex 1 and H 2 O 2 , attempting to isolate the porphyrin product in the reaction and examine its reactivity toward stoichiometric epoxidation of alkenes. Treatment of 1 with excess H 2 O 2 in dichloromethane-methanol (8:2 v/v) resulted in a slow colour change of the mixture from green to red brown.…”

Section: Asymmetric Epoxidation Of Aromatic Alkenes With Tbhp Catalysed By Complexmentioning

confidence: 99%

“…However, to our knowledge, all the reported complexes bear non-chiral porphyrin macrocycles, which prevents them from functioning as catalysts in asymmetric catalysis. Indeed, while a few alkene epoxidations catalysed by molybdenum porphyrins have been reported [7][8][9], none of them are enantioselective. We also note that these epoxidation studies are focused on aliphatic or cyclic alkenes (such as hexenes and cyclooctene) [7][8][9] and attempts to epoxidise an aromatic alkene (such as styrene) with hydrogen peroxide by employing catalysts [Mo V (O)(tpp)(X)] (tpp= meso-tetraphenylporphyrinato dianion, X= Cl, OH, OMe, OAc, SCN) have failed [8].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and X-ray crystal structure of a chiral molybdenum porphyrin and its catalytic behaviour toward asymmetric epoxidation of aromatic alkenes

Liu

Zhang

Huang

et al. 2001

Journal of Organometallic Chemistry

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“…In this case the two requirements, anhydrous hydrogen peroxide and the need for a cosolvent, could be met by using hydrogen peroxide in EtOAc, easily prepared by azeotropic drying. 6 Table 2 shows the results for epoxidation of several alkenes catalyzed by perfluoroheptadecan-9-one in refluxing 1,2-dichloroethane. Most epoxides are obtained in excellent yields, except for extremely acid-sensitive epoxides like camphene oxide and a-pinene oxide.…”

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confidence: 99%