Ruthenium meso-Tetrakis(2,6-dichlorophenyl)porphyrin Complex Immobilized in Mesoporous MCM-41 as a Heterogeneous Catalyst for Selective Alkene Epoxidations.
Ruthenium meso-Tetrakis(2,6-dichlorophenyl)porphyrin Complex Immobilized in Mesoporous MCM-41 as a Heterogeneous Catalyst for Selective Alkene Epoxidations.
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DOI：
10.1021/jo981003l
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发表时间：
1998-09
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影响因子：
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通讯作者：
Chun-Jing Liu;Wing-Yiu Yu;Shougui Li;C. Che
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文献类型：
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作者：
Chun-Jing Liu;Wing-Yiu Yu;Shougui Li;C. Che
介孔MCM-41分子筛固定化了介孔四（2,6-二氯苯）卟啉钌配合物[Ru(II)(TDCPP)(CO)(EtOH)]；负载型Ru催化剂以2,6-二氯吡啶n -氧化物为末端氧化剂，可实现高选择性烯烃非均相环氧化反应。芳香族和脂肪族烯烃能以较高的收率和选择性高效地转化为环氧化物，顺式烯类如顺式二苯乙烯、顺式- - -甲基苯乙烯和顺式- - -氘苯乙烯被立体特异性地环氧化。在非均相钌催化下，降冰片烯和环烯等环烯烃的氧化可以有效地进行，而这些烯烃在沸石基硅酸钛（TS-1）催化条件下无反应（Murugavel， R.; Roesky， H. W. Angew）。化学。, Int。编辑。英语。1997,36,477)。另一方面，Ru/ m -41(m)催化剂在(+)-柠檬烯氧化中表现出尺寸选择性，末端C=C键（相对于内部三取代的C=C键）更容易被氧化。体积庞大的3,4,6-三- o -苄基- d -葡聚糖在异相钌催化条件下无法反应，而较小的乙酰基衍生物则转化为3:1的α -和β -环氧化合物混合物。Ru/ m -41(m)催化剂可以重复使用，在11 691次循环（3次循环）后，其初始活性仍保持67%。活性损失归因于催化剂浸出和/或失活。根据Hammett相关（rho(+) = -0.72, R = 0.997）和产物研究（环己烯和顺式烯烃为底物），反应性二氧化锆（VI）卟啉中间体不受青睐。氧(V)配合物或氧（IV）卟啉阳离子自由基可能是这种高选择性环氧化反应的关键中间体。
A ruthenium complex of meso-tetrakis(2,6-dichlorophenyl)porphyrin, [Ru(II)(TDCPP)(CO)(EtOH)], is immobilized into mesoporous MCM-41 molecular sieves; the supported Ru catalyst can effect highly selective heterogeneous alkene epoxidations using 2,6-dichloropyridine N-oxide as terminal oxidant. Aromatic and aliphatic alkenes can be efficiently converted to their epoxides in good yields and selectivities, and cis-alkenes such as cis-stilbene, cis-beta-methylstyrene, and cis-beta-deuteriostyrene are epoxidized stereospecifically. Oxidation of cycloalkenes, e.g., norbornene and cyclooctene, can be carried out effectively using the heterogeneous Ru-catalyzed reaction while these alkenes are unreactive in the zeolite-based titanium silicate (TS-1)-catalyzed conditions (Murugavel, R.; Roesky, H. W. Angew. Chem., Int. Ed. Engl. 1997, 36, 477). On the other hand, the Ru/M-41(m) catalyst displays size selectivity in the (+)-limonene oxidation where the terminal C=C bond (vs internal trisubstituted C=C bond) becomes more readily oxidized. Bulky 3,4,6-tri-O-benzyl-D-glucal has failed to react under the heterogeneous Ru-catalyzed conditions, whereas the smaller acetyl derivative is converted to a 3:1 mixture of alpha- and beta-glycal epoxides. The Ru/M-41(m) catalyst can be used repeatedly, and 67% of its initial activity is retained after 11 691 turnovers (three runs). The loss of activity is attributed to catalyst leaching and/or deactivation. On the basis of Hammett correlation (rho(+) = -0.72, R = 0.997) and product studies (cyclohexene and cis-alkenes as the substrates), a reactive dioxoruthenium(VI) porphyrin intermediate is not favored. An oxoruthenium(V) complex or oxoruthenium(IV) porphyrin cation radical could be the key intermediate for this highly selective epoxidation reaction.