Olefin epoxidation by a (salen)Mn(iii) catalyst covalently grafted on glass beads

Abstract

The asymmetric epoxidation of unfunctionalized prochiral olefins catalyzed by chiral (salen)Mn(III) complexes is an important viable route to obtain chiral epoxides. Recently we proposed a monolayer of (salen)Mn(III) molecules on functionalized flat silica substrates as an active heterogeneous catalyst for enantioselective epoxidation of 6-cyano-2,2-dimethylchromene with huge turnover values. In the present study we synthesized a monolayer of modified (salen)Mn(III) molecules on previously functionalized glass bead substrates in order to increase the active surface area. The catalyst activity of this system was tested with different olefins and in some cases we observed enantioselectivity higher than in solution. The system was reused up to seven times with no variation in performance.

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].…”

Chiral Salen Complexes for Asymmetric Heterogeneous Catalysis: Recent Examples for Recycling and Cooperativity

“…Other supports have also been involved in asymmetric heterogeneous catalysis and a Mn‐salen monolayer was for instance attached on glass bead substrates, via a covalent link after glass silylation ( 4 in Scheme ) . Used in the asymmetric epoxidation of alkenes (4 examples) this catalyst reached high yield and ee values and the beads were reused without loss of their productivity in up to 7 cycles.…”

“…[14] Other supports have also been involved in asymmetric heterogeneous catalysis and a Mn-salen monolayer was for instance attached on glass bead substrates, via a covalent link after glass silylation (4 in Scheme 2). [15] Used in the asymmetric epoxidation of alkenes (4 examples) this catalyst reached high yield and ee values and the beads were reused without loss of their productivity in up to 7 cycles. To facilitate separation of potentially too fine particles and improve dispersion of the catalyst within the reaction medium, Mn-salen complexes were also immobilized on membranes.…”

Nerve Gas Simulant Sensing by a Uranyl–Salen Monolayer Covalently Anchored on Quartz Substrates

“…UV/Vis spectra of a3 86. 10 À6 m solution of Sal-UO 2 -CH 2 OH in toluene/CH 3 CN (50:50 v/v;red line); U_Salen_SAM (black line); U_Salen_SAM after immersioninC HCl 3 (25 mL) containingD MMP(2mL, 0.008 %v /v), washed with CHCl 3 and dried under nitrogen (blue line);and after heating as-synthesized U_Salen_SAM at 1208 Cf or 24 h(green line).…”

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Au ranyl complex monolayert hat easily allows the opticald etection of an erve gas simulant, namely,d imethyl methylphosphonate, is reported. Both UV/Viss pectroscopy and photoelectrond ata confirm that the functional hybrid materialc oordinates aL ewis base by means of the P=O group, which interacts with the uranium equatorial site available for complexation.Scheme2.Synthesis of Sal-UO 2 -CH 2 OH.R eagents and conditions: a) formaldehyde (37 %a queoussolution), concentrated HCl, 70 8C, 24 h, 40 %; b) CuSO 4 ,H 2 O/DMSO( 1/2), 110 8C, 2h,9 5%;c)diphenylethylendiamine chlorohydrate, [86][87][88][89] EtOH/MeOH( 1/1),R T, 24 h, 50 %; d) 1,Et 3 N, EtOH, 60 8C, 24 h, 47 %; e) UO 2 (AcO) 2 ·2H 2 O, EtOH, RT,24h,9 0%.

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