(Salen)Mn(III) Catalyzed Asymmetric Epoxidation Reactions by Hydrogen Peroxide in Water: A Green Protocol

Abstract

Enantioselective epoxidation reactions of some chosen reactive alkenes by a chiral Mn(III) salen catalyst were performed in H2O employing H2O2 as oxidant and diethyltetradecylamine N-oxide (AOE-14) as surfactant. This procedure represents an environmentally benign protocol which leads to e.e. values ranging from good to excellent (up to 95%).

A New Mn–Salen Micellar Nanoreactor for Enantioselective Epoxidation of Alkenes in Water

“…Enantiomeric excess values with 1,2-dihydronaphthalene were also in the range of 80-84%, confirming the ability of the nanoreactor to achieve enantioselectivity. As shown in our previous works [17,18], 1,2-dihydronaphthalene presents lower reaction rates compared to 6-cyano-2,2-dimethylchromene. In fact, under the same conditions, after 1 h of reaction, only a 17% conversion was obtained (Entry 1 vs.…”

“…We selected a cationic surfactant to obtain a micellar surface fully covered by the same positive charges. In addition, catalyst was designed in order to confine the catalytic metal center inside the hydrophobic region of the nanoreactor (see Figure 1), in contrast with our previous works where it was located on the Stern layer [17,18]. We think the catalytic site sequestered in the interior of micelles should lead to higher reaction rates, due to a proximity effect with the alkene inside the core of a micelle.…”

Supramolecular Detection of a Nerve Agent Simulant by Fluorescent Zn–Salen Oligomer Receptors

“…Metal–Salen complexes are well known in literature for their use as catalysts [26,27,28,29,30] and supramolecular hosts [31,32,33,34,35,36,37,38], where the Lewis acid metal center is exploited for the recognition of Lewis base species. Furthermore, recently we also demonstrated the high efficiency of metal-Salen complexes as receptors for NA simulants [25,39].…”

Influence of Impurities in a Methanol Solvent on the Epoxidation of Propylene with Hydrogen Peroxide over Titanium Silicalite-1

“…In fact, due to the highest active oxygen content and the formation of water only being a by-product, the use of H 2 O 2 as an oxidant is among the key aspects of modern Green Chemistry nowadays. For example, H 2 O 2 has become the primary oxidant in the selective oxidations of numerous organic substances, such as imines [20], olefins [21][22][23], and alcohols [24].In recent years, the HPPO process based on a TS-1 catalyst, as well as the H 2 O 2 oxidant and methanol solvent, has been industrialized by BASF and Dow, Evonik and Uhde, and Sinopec Changling Refining and Chemical. Nevertheless, the HPPO process still suffers from the use of a methanol solvent.…”

“…In fact, due to the highest active oxygen content and the formation of water only being a by-product, the use of H 2 O 2 as an oxidant is among the key aspects of modern Green Chemistry nowadays. For example, H 2 O 2 has become the primary oxidant in the selective oxidations of numerous organic substances, such as imines [20], olefins [21][22][23], and alcohols [24].…”