Solvent-free oxidation reactions with Ti-MCM-41 and TS-1 catalysts occluded in polydimethylsiloxane (PDMS) membranes

Abstract

The incorporation of TS-1 and Ti-MCM-41 catalysts in PDMS is proven to enable the oxidation of hexane and epoxidation of cis-cyclooctene, respectively, with high conversions under solvent-free reaction conditions.

Solvent free permanganate oxidations

“…[1][2][3][4][5][6][7][8][9][10][11][12] In this paper we wish to describe a simple and general procedure that can be used for the oxidative transformation of many organic functional groups using an inexpensive and environmentally friendly oxidant, potassium permanganate. 13 Best results are obtained when KMnO 4 is first mixed with copper sulfate pentahydrate (or a 20/80 mixture of copper sulfate pentahydrate and alumina) to give a reagent that has previously been used extensively as a heterogeneous oxidant in inert solvents.…”

New selectivities from old catalysts. Occlusion of Grubbs’ catalysts in PDMS to change their reactions

“…This work allows one to choose to react substrates by metathesis or isomerization by whether the catalysts are occluded or not. In addition, this work is a part of an ongoing research program in our lab and others to occlude catalysts in PDMS to study their reactivity [19,34]. PDMS is an interesting matrix for catalysts as it allows small molecules to diffuse into it, is apolar, and can be readily molded into many different shapes.…”

Aspects of Immobilisation of Catalysts on Polymeric Supports

“…[188] In the absence of a solvent, undesired blank reactions were suppressed and the absence of water in the catalyst pores limited the epoxide ring opening in epoxidations. [189,190] However, consecutive oxidation reactions gained importance as no solvent was present to remove the products from the catalyst pores. [189] Reaction rates could be increased by adding modifiers to the membrane [191] or by blending hydrophilic polymers with the PDMS, improving the balance between the sorbed amounts of peroxide and alkane.…”

“…[189,190] However, consecutive oxidation reactions gained importance as no solvent was present to remove the products from the catalyst pores. [189] Reaction rates could be increased by adding modifiers to the membrane [191] or by blending hydrophilic polymers with the PDMS, improving the balance between the sorbed amounts of peroxide and alkane. [192] Whereas ethyl acrylate-based pseudo-interpenetrating networks as polymer systems used for catalyst incorporation, avoided membrane cracks upon zeolite incorporation, active sites were more blocked by the penetrated polymer chains.…”