Polymeric catalysts for chemo- and enantioselective epoxidation of olefins: New crosslinked chiral transition metal complexing polymers

Abstract

Polymeric analogs of well‐known chiral Mn(III)‐salen complexes were synthesized and were used as recyclable catalysts for asymmetric epoxidation of olefins. For this purpose two different monomers, 2 and 3, bearing chiral Mn(III)‐salen moieties were synthesized. The monomer 3 carries a bulky substituent closer to the Schiff base moiety, while monomer 2 lacks such a substituent. These metal complexed chiral monomers were subsequently copolymerized with ethylene glycol dimethacrylate producing insoluble crosslinked functional matrices that possess macroporous morphology. Chemo‐ and enantioselective catalytic activities of these two polymers were evaluated for epoxidation of olefins. Both polymers catalyzed the epoxidation of a variety of olefins at room temperature in the presence of iodosylbenzene (PhIO) as the terminal oxidant with yields comparable to the homogenous system. In terms of their enantioselective catalytic activity, polymer P‐2 (obtained from 3) performed better than polymer P‐1 (obtained from 2). Unfortunately, while the homogeneous systems are reported to offer over 80% enantioselectivity, with the present polymeric catalysts, enantioselectivity to a maximum of 30% were observed. Unlike the homogeneous system, use of an external nitrogenous donor played a very insignificant role in influencing enantioselectivity. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1809–1818, 1997

Highly enantioselective resolution of terminal epoxides with cross-linked polymeric salen–Co(III) complexes

“…22 (Scheme 1) The key dialdehyde 9 and trialdehyde 10 were synthesized through the condensation of 3-tert-butyl-2,5-dihydroxybenzaldehyde with diacid and triacid derived from hydroquinone and chloroglucinol (Scheme 2). The condensation of aldehyde and (R,R)-1,2-diaminocyclohexane stoichiometrically afforded the polymeric ligands.…”

Highly enantioselective resolution of terminal epoxides with cross-linked polymeric salen–Co(III) complexes

“…22 (Scheme 1) The key dialdehyde 9 and trialdehyde 10 were synthesized through the condensation of 3-tert-butyl-2,5-dihydroxybenzaldehyde with diacid and triacid derived from hydroquinone and chloroglucinol (Scheme 2). The condensation of aldehyde and (R,R)-1,2-diaminocyclohexane stoichiometrically afforded the polymeric ligands.…”

Synthesis and characterization of new chiral ketopinic acid-derived catalysts immobilized on polystyrene-bound imidazole

“…Heterogeneous catalysis has the potential advantages of easy separation, efficient recycling, and the minimization of metal trace in the product. There are also improved handling and process control issues that could, in principle, result in an overall reduction of costs and waste [14,15]. Scheme 1.…”

Integration of on‐column catalysis and EKC analysis: Investigation of enantioselective sulfoxidations

“…Catalyst immobilization often offers the advantage of being easy to recycle, often showing increased stability and the possibility to be used in flow‐through processes . Salen‐type catalysts have been immobilized on various organic polymers , hybrid polymers, mesoporous materials and zeolites , and membranes .…”

Highly enantioselective resolution of terminal epoxides with cross-linked polymeric salen–Co(III) complexes

“…22 (Scheme 1) The key dialdehyde 9 and trialdehyde 10 were synthesized through the condensation of 3-tert-butyl-2,5-dihydroxybenzaldehyde with diacid and triacid derived from hydroquinone and chloroglucinol (Scheme 2). The condensation of aldehyde and (R,R)-1,2-diaminocyclohexane stoichiometrically afforded the polymeric ligands.…”

Synthesis and characterization of new chiral ketopinic acid-derived catalysts immobilized on polystyrene-bound imidazole

“…Heterogeneous catalysis has the potential advantages of easy separation, efficient recycling, and the minimization of metal trace in the product. There are also improved handling and process control issues that could, in principle, result in an overall reduction of costs and waste [14,15]. Scheme 1.…”

Integration of on‐column catalysis and EKC analysis: Investigation of enantioselective sulfoxidations

“…Catalyst immobilization often offers the advantage of being easy to recycle, often showing increased stability and the possibility to be used in flow‐through processes . Salen‐type catalysts have been immobilized on various organic polymers , hybrid polymers, mesoporous materials and zeolites , and membranes .…”

Highly enantioselective resolution of terminal epoxides with cross-linked polymeric salen–Co(III) complexes

“…22 (Scheme 1) The key dialdehyde 9 and trialdehyde 10 were synthesized through the condensation of 3-tert-butyl-2,5-dihydroxybenzaldehyde with diacid and triacid derived from hydroquinone and chloroglucinol (Scheme 2). The condensation of aldehyde and (R,R)-1,2-diaminocyclohexane stoichiometrically afforded the polymeric ligands.…”

Synthesis and characterization of new chiral ketopinic acid-derived catalysts immobilized on polystyrene-bound imidazole

“…Heterogeneous catalysis has the potential advantages of easy separation, efficient recycling, and the minimization of metal trace in the product. There are also improved handling and process control issues that could, in principle, result in an overall reduction of costs and waste [14,15]. Scheme 1.…”

Integration of on‐column catalysis and EKC analysis: Investigation of enantioselective sulfoxidations

“…Catalyst immobilization often offers the advantage of being easy to recycle, often showing increased stability and the possibility to be used in flow‐through processes . Salen‐type catalysts have been immobilized on various organic polymers , hybrid polymers, mesoporous materials and zeolites , and membranes .…”