Asymmetric Catalysis by Heterogeneous Catalysts

Coman, Simona M.; Poncelet, Georges; Pârvulescu, Vasile I.

doi:10.1002/chin.200714251

Cited by 1 publication

(1 citation statement)

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“…Besides this, one of the problems that is frequently questionable in the immobilization of a catalyst in inorganic supports, is the leaching of the catalyst due to the instability of the support-catalyst bond [21]. It is wellknown that the reuse of an immobilized catalyst is simpler with respect to its homogenous counterpart, however, in some cases this can necessarily be preceded by the reactivation of the catalyst, when this is deactivated either by poisoning, fouling, thermal degradation or volatilization of the active components [19,22].…”

Section: Introductionmentioning

confidence: 99%

Enantioselective epoxidation of styrene using in-situ generated dimethyldioxirane and dimeric homochiral Mn(III)-Schiff base complex catalyst

Verdugo-Torres

Cubillos-Lobo

Rojas

2018

Rev.Fac.Ing.Univ.Antioquia

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The enantioselective epoxidation of styrene using in-situ generated dimethyldioxirane (DMD) and dimeric homochiral Mn(III)-Schiff base catalyst 1 has been explored. The parameters evaluated were olefin/oxidant molar ration, catalyst loading, reaction temperature and presence of nitrogen coordinating co-catalysts. Conversions of more than 99% and enantiomeric excess 66% were obtained. The selectivity is complete towards styrene oxide using 2 mol% catalyst loading, 1.36 mmol KHSO 5 in 8 ml of water, absence of co-catalyst and 17°C as reaction temperature. Furthermore, the catalyst could be recycled up to three times with slightly decrease of catalytic activity due mainly to the physical loss of the catalyst during the recovery step and at a lesser extent as a consequence of its oxidative degradation. RESUMEN: Se ha explorado la epoxidación enantioselectiva de estireno utilizando dimetildioxirano (DMD) generado in-situ y un complejo de base de Schiff homoquiral dimérico de Mn (III). Los parámetros evaluados fueron la relación molar olefina/oxidante, la cantidad de catalizador, la temperatura de reacción y la presencia de co-catalizadores coordinadores de nitrógeno. Se obtuvieron conversiones por encima de 99% y excesos enantioméricos cercanos al 66%. La reacción fue completamente selectiva hacia el óxido de estireno usando 2% en moles de carga de catalizador, 1.36 mmol de KHSO 5 en 8 ml de agua, ausencia de cocatalizador y 17ºC como temperatura de reacción. Además, el catalizador puede reutilizarse hasta tres veces con una leve disminución de la actividad catalítica debido principalmente, a la pérdida física del catalizador durante la etapa de recuperación del catalizador, y en menor medida a su degradación oxidativa.

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Section: Introductionmentioning

confidence: 99%