Immobilized dimeric chiral Mn(III) salen complex on short channel ordered mesoporous silica as an effective catalyst for the epoxidation of non-functionalized alkenes

Ordered short channel mesoporous silica modified with 1,3,5-triazine–piperazine as a versatile recyclable basic catalyst for cross-aldol, Knoevenagel and conjugate addition reactions with isatins

“…10 Despite the significant success in nucleophilic substitution reactions of isatins, there is still sufficient room for improvement, particularly in terms of catalyst loading and its recovery and reuse. 19 In order to overcome the diffusional constrains often associated with such silica materials, the silica used in this case was short channel periodic Piperazine, in particular, has shown interesting properties as an organocatalyst in nucleophilic substitution reactions of carbonyl compounds owing to its ability to form enamine, which is thought to be the reactive intermediate for aldol condensation.…”

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

“…In these cases enantiomeric excess values are similar to our data obtained in solution (Table S1 †) and similar to recently reported results. [40][41][42][43][44][45] An interesting observation is the high present value of the turnover frequencies under heterogeneous conditions (1.24 × 10 5 using 10 spheres) with respect to the solution (20) after total olefin transformation. 20,21,41 Obviously, the highest TON values have been observed for the lowest number of beads used in the reaction media (Tables 1-4).…”

Green synthesis of 6-cyano-2,2-dimethyl-2-H-1-benzopyran and its subsequent enantioselective epoxidation

“…The possibility of recycling the catalyst was also examined and no appreciable loss of catalytic activity was observed after four cycles (Table 2, entries 5, [9][10][11]; product yield varied between 38 and 36%. -120 12 ---2 PMo12 1 120 12 ---3 PMo11V 1 120 12 ---4 Py3- PMo11V 1 120 12 37 90 33 5 Py3-PMo11V 1 120 6 38 92 35 6 Py3- PMo11V 1 100 12 5 100 5 7 Py3- PMo11V 1 80 12 ---8 Py3- PMo11V 2 120 6 34 94 32 9 Py3 In order to assess the possible catalyst solubilization, additional tests were performed.…”

“…Due to the intrinsic advantages of heterogeneous catalysis, i.e., easy catalyst separation and recycling as well as product separation [9], some homogeneous chiral catalysts has been used in a two-phase system or they have been anchoring on a solid support. It is generally believed that the immobilization of chiral salen manganese(III) complexes onto solid supports could isolate the catalytically active intermediate species Mn(V)-oxo, which might greatly reduce the formation of inactive -oxoMn(IV) dimers and increase catalyst stability [10]. Unfortunately, in comparison with their homogeneous counterparts, the immobilized complexes often exhibit poor activity, leaching of the active species, or low accessibility to substrates [11].…”

“…Unfortunately, in comparison with their homogeneous counterparts, the immobilized complexes often exhibit poor activity, leaching of the active species, or low accessibility to substrates [11]. These limitations seem to be well assessed by using a high ordered short hexagonal channel mesoporous support, modified with a long chain melamine-piperazine linker, which allows the immobilization of a type of dimeric chiral Mn(III) salen complex by covalent bonds [10]. As a second approach, the modification of the highly soluble http://dx.doi.org/10.1016/j.molcata.2014.11.027 1381-1169/© 2014 Elsevier B.V. All rights reserved.…”