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Table 1. Epoxidation reactions catalyzed by different Mn-salen catalysts by Reger and Janda.!*!! lal Reaction conditions: MCPBA (2 equiv.), NMO (5 equiv.), catalyst (4 mol %), 0°C. (1 Enantiomeric excess determined by 'H NMR in the presence of the chiral shift reagent Eu(hfc);. (cl Tsolated yield. \4] The enantiomeric excess of the cis-epoxide as determined by GC analysis using Chiraldex G-TA chiral colun

Table 1 Epoxidation reactions catalyzed by different Mn-salen catalysts by Reger and Janda.!*!! lal Reaction conditions: MCPBA (2 equiv.), NMO (5 equiv.), catalyst (4 mol %), 0°C. (1 Enantiomeric excess determined by 'H NMR in the presence of the chiral shift reagent Eu(hfc);. (cl Tsolated yield. \4] The enantiomeric excess of the cis-epoxide as determined by GC analysis using Chiraldex G-TA chiral colun

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Robert E. Ziegert (left) was born in Berlin, Germany in 1973. He studied at the University of Dortmund where he received his degree in 2001 in the group of B. Schmidt. Currently, he is a Ph. D. student at the University of Bonn in the group of S. Brase. His research topics are studies on the asymmetric opening of bicyclic endo- peroxides, asymmetric 1,2-addition reaction on solid support and spectroscopic studies on diethylzinc/ paracyclophane based N,O-ligand complexes.
Robert E. Ziegert (left) was born in Berlin, Germany in 1973. He studied at the University of Dortmund where he received his degree in 2001 in the group of B. Schmidt. Currently, he is a Ph. D. student at the University of Bonn in the group of S. Brase. His research topics are studies on the asymmetric opening of bicyclic endo- peroxides, asymmetric 1,2-addition reaction on solid support and spectroscopic studies on diethylzinc/ paracyclophane based N,O-ligand complexes.
Scheme 1. Recycling scheme for a polymer-supported chiral ligand.
Scheme 1. Recycling scheme for a polymer-supported chiral ligand.
of supports are able to swell in some organic solvents increasing their inner surface. Therefore, the catalytic activity is significantly enhanced. The recycling and reuse of insoluble organic polymer resins are easily performed by filtration techniques. Soluble organic polymer and dendritic chiral ligands could be recovered by precipitation. In general, their catalytic activity is higher compared to solid-bound catalysts.
of supports are able to swell in some organic solvents increasing their inner surface. Therefore, the catalytic activity is significantly enhanced. The recycling and reuse of insoluble organic polymer resins are easily performed by filtration techniques. Soluble organic polymer and dendritic chiral ligands could be recovered by precipitation. In general, their catalytic activity is higher compared to solid-bound catalysts.
Figure 4. Monomeric and polymeric catalysts 16a-—e and poly-16a-—c prepared by Salvadori et al.' Figure 3. First polymer-supported Jacobsen catalyst 15 of Sivaram, Dhal et al.!*¢!
Figure 4. Monomeric and polymeric catalysts 16a-—e and poly-16a-—c prepared by Salvadori et al.' Figure 3. First polymer-supported Jacobsen catalyst 15 of Sivaram, Dhal et al.!*¢!
Figure 2. Titanium(IV)-silsesquioxane complex 13 of Abben- huis et al.54l and solid-supported complex 14 of Jacobs et al.
Figure 2. Titanium(IV)-silsesquioxane complex 13 of Abben- huis et al.54l and solid-supported complex 14 of Jacobs et al.
Figure 5. Dimeric Mn(III)-salen complex 17 prepared by Janssen et al.6755)
Figure 5. Dimeric Mn(III)-salen complex 17 prepared by Janssen et al.6755)
Figure 6. Polystyrene and polymethacrylate based polymer- supported Jacobsen catalysts 18a—e by Sherrington et al.'**! and 19a—e by Reger and Janda|!*!]
Figure 6. Polystyrene and polymethacrylate based polymer- supported Jacobsen catalysts 18a—e by Sherrington et al.'**! and 19a—e by Reger and Janda|!*!]
Catalyst loadings of 19c ranging from 0.70- 0.75 mmol/g causing constant enantioselectivies of 51% (styrene) and 88% (methylstyrene) were observed. The recycling of the catalysts gave moderate yields, while the selectivity decreases after the second run. reactions.!°'] The complex 18e (Figure 5) and the cata- lysts shown in Figure 20 and Table 1 were examined for epoxidation reactions of styrene, cis-methylstyrene and dihydronaphthalene with MCPBA.
Catalyst loadings of 19c ranging from 0.70- 0.75 mmol/g causing constant enantioselectivies of 51% (styrene) and 88% (methylstyrene) were observed. The recycling of the catalysts gave moderate yields, while the selectivity decreases after the second run. reactions.!°'] The complex 18e (Figure 5) and the cata- lysts shown in Figure 20 and Table 1 were examined for epoxidation reactions of styrene, cis-methylstyrene and dihydronaphthalene with MCPBA.
Table 2. Asymmetric epoxidation reaction of 1,2-dihydronaphthalene (26) using catalysts 25 by Smith and Liu.
Table 2. Asymmetric epoxidation reaction of 1,2-dihydronaphthalene (26) using catalysts 25 by Smith and Liu.
Scheme 2. Preparation of silica gel-supported salen complexes 24a-n by Seebach et al. tioselectivities and yields were comparable with the soluble Mn-salen complex-catalyzed reaction (up to 75% ee, yield up to 95%). The reuse of the catalysts showed only a small difference of the selectivity (around 10% lower), but the yields decreased in some cases from quantitative to 60% after the seventh run.
Scheme 2. Preparation of silica gel-supported salen complexes 24a-n by Seebach et al. tioselectivities and yields were comparable with the soluble Mn-salen complex-catalyzed reaction (up to 75% ee, yield up to 95%). The reuse of the catalysts showed only a small difference of the selectivity (around 10% lower), but the yields decreased in some cases from quantitative to 60% after the seventh run.
Figure 10. Olefins 30a-—f used in epoxidation reactions by Che et al! Scheme 3. Epoxidation catalysis using porphyrin 31-[G—n],, by Che et al.{*7
Figure 10. Olefins 30a-—f used in epoxidation reactions by Che et al! Scheme 3. Epoxidation catalysis using porphyrin 31-[G—n],, by Che et al.{*7
Figure 9. D,-symmetric chiral dichlororuthenium(VI) porphyrin catalysts 28 and 29 by Che et al.!®!
Figure 9. D,-symmetric chiral dichlororuthenium(VI) porphyrin catalysts 28 and 29 by Che et al.!®!
Figure 12. Chiral tartrate ester incorporated within a poly- meric framework 34 by Sherrington et al.!®! Figure 11. Schematic structures of a dendritic ruthenium porphyrin 31-[G—7]s by Che et al.!°7
Figure 12. Chiral tartrate ester incorporated within a poly- meric framework 34 by Sherrington et al.!®! Figure 11. Schematic structures of a dendritic ruthenium porphyrin 31-[G—7]s by Che et al.!°7
Scheme 4. Synthesis of the silica-supported alkoxytantalum compounds 37a,b and 38a,b by de Mallmann, Basset et al. (NpH = neopentane).!!)
Scheme 4. Synthesis of the silica-supported alkoxytantalum compounds 37a,b and 38a,b by de Mallmann, Basset et al. (NpH = neopentane).!!)
Scheme 5. Weitz—Scheffer epoxidation catalyzed by polymer- ic amino acids reported by Julid and Colonna.!!
Scheme 5. Weitz—Scheffer epoxidation catalyzed by polymer- ic amino acids reported by Julid and Colonna.!!
Figure 13. 6-Amino acids 43, 44 and TentaGel-bounc oligomers poly-43 und 44 by Berkessel et al.!”4I
Figure 13. 6-Amino acids 43, 44 and TentaGel-bounc oligomers poly-43 und 44 by Berkessel et al.!”4I
Scheme 6. Possible application of salen complex 45 in com- binatorial synthesis.!”7! Table 5. HKR of racemic epichlorhydrin (46) catalyzed by salen complex 45 (for details see Jacobsen et alll),
Scheme 6. Possible application of salen complex 45 in com- binatorial synthesis.!”7! Table 5. HKR of racemic epichlorhydrin (46) catalyzed by salen complex 45 (for details see Jacobsen et alll),
Figure 15. Silica-supported Co(salen) complex 54 for contin- uous-flow HKR by Jacobsen et al.!77!
Figure 15. Silica-supported Co(salen) complex 54 for contin- uous-flow HKR by Jacobsen et al.!77!
Table 6. Catalytic enantioselective addition of TMSCN to meso-epoxides by Hoveyda et al.!”5]
Table 6. Catalytic enantioselective addition of TMSCN to meso-epoxides by Hoveyda et al.!”5]
Figure 16. Optimized ligands 55-57 for catalytic enantiose- lective addition of TMSCN to meso-epoxides by Hoveyda et al.!78!
Figure 16. Optimized ligands 55-57 for catalytic enantiose- lective addition of TMSCN to meso-epoxides by Hoveyda et al.!78!
Scheme 7. Asymmetric dihydroxylation reaction by Sharpless et al.
Scheme 7. Asymmetric dihydroxylation reaction by Sharpless et al.
Table 7. Asymmetric dihydroxylation reaction™! with ligand 60 by Janda et al.!*4]
Table 7. Asymmetric dihydroxylation reaction™! with ligand 60 by Janda et al.!*4]
Table 8. Asymmetric dihydroxylation reaction! with ligands 61a, b and 62 by Bolm et al.!*4
Table 8. Asymmetric dihydroxylation reaction! with ligands 61a, b and 62 by Bolm et al.!*4
Figure 19. Modified cinchona alkaloids on an_ insoluble inorganic support 63a, b and 64a, b by Bolm et al.!®*!
Figure 19. Modified cinchona alkaloids on an_ insoluble inorganic support 63a, b and 64a, b by Bolm et al.!®*!
Table 9. Asymmetric dihydroxylation reaction! with ligands 63a, b and 64a, b by Bolm et al.!®*! lal Conditions: see ref.!%!
Table 9. Asymmetric dihydroxylation reaction! with ligands 63a, b and 64a, b by Bolm et al.!®*! lal Conditions: see ref.!%!
Table 10. Asymmetric dihydroxylation reaction! of olefins using PEM-MC OsO, 65 by Kobayashi et al.!°7]
Table 10. Asymmetric dihydroxylation reaction! of olefins using PEM-MC OsO, 65 by Kobayashi et al.!°7]
K;Fe(CN).¢ or molecular oxygen a deactivation was observed.
K;Fe(CN).¢ or molecular oxygen a deactivation was observed.
Table 11. Results of solvent effect on the LDH-OsO, 67 catalyzed asymmetric dihydroxylation of trans-stilbene"! reported by Choudary et al.!°)
Table 11. Results of solvent effect on the LDH-OsO, 67 catalyzed asymmetric dihydroxylation of trans-stilbene"! reported by Choudary et al.!°)
Scheme 9. Immobilization of bis(oxazolines) to give organic polymers 69-72 by Mayoral et al.!4!J
Scheme 9. Immobilization of bis(oxazolines) to give organic polymers 69-72 by Mayoral et al.!4!J
Scheme 10. Cyclopropanation reaction catalyzed by immobi- lized catalysts 6a, 6f, 69a-72a and 70b-72b by Mayoral et al.)
Scheme 10. Cyclopropanation reaction catalyzed by immobi- lized catalysts 6a, 6f, 69a-72a and 70b-72b by Mayoral et al.)
Table 12. Cyclopropanation reaction"! between styrene (30a) and ethyl diazoacetate (73) catalyzed by the immobilizec catalysts 69a—72a and 70b-—72b by Mayoral et al.!*!]
Table 12. Cyclopropanation reaction"! between styrene (30a) and ethyl diazoacetate (73) catalyzed by the immobilizec catalysts 69a—72a and 70b-—72b by Mayoral et al.!*!]
Scheme 11. Immobilization of bis(oxazoline) copper complexes 76a-—d-Cu(OTf), and 77a-d-Cu(OTf), onto silica by Mayoral et al.!*7!
Scheme 11. Immobilization of bis(oxazoline) copper complexes 76a-—d-Cu(OTf), and 77a-d-Cu(OTf), onto silica by Mayoral et al.!*7!
Table 13. Cyclopropanation reaction"! between styrene (30a) and ethyl diazoacetate (73) catalyzed by silica-based catalysts reported by Mayoral et al.!*!
Table 13. Cyclopropanation reaction"! between styrene (30a) and ethyl diazoacetate (73) catalyzed by silica-based catalysts reported by Mayoral et al.!*!
'] For reaction conditions and analysis see ref.) (h] Reused catalyst. Table 14. Cyclopropanation reaction between styrene (30a) and ethyl diazoacetate (73) catalyzed by polymeric catalysts!! by Mayoral et al.417]
'] For reaction conditions and analysis see ref.) (h] Reused catalyst. Table 14. Cyclopropanation reaction between styrene (30a) and ethyl diazoacetate (73) catalyzed by polymeric catalysts!! by Mayoral et al.417]
Scheme 12. Preparation of polymeric bis(oxazoline) ligands 80-88 by grafting and polymerization by Mayoral et al.(4!“7]
Scheme 12. Preparation of polymeric bis(oxazoline) ligands 80-88 by grafting and polymerization by Mayoral et al.(4!“7]
Scheme 13. Preparation of polymers with bis(oxazoline) ligands in the polymers chain 89 and 90 by Mayoral et al.!417]
Scheme 13. Preparation of polymers with bis(oxazoline) ligands in the polymers chain 89 and 90 by Mayoral et al.!417]
Scheme 15. Asymmetric cyclopropanation reaction of styrene (30a) with the ligands 94a—e and 95 by Reiser and Glos.!“4] Scheme 14. Synthesis of new aza-bis(oxazoline) ligands 93a, b and 94a—c and the immobilization of 93b by Reiser and Glos. Table 15. Asymmetric cyclopropanation reaction! of styrene (30a) by Reiser and Glos.!“!
Scheme 15. Asymmetric cyclopropanation reaction of styrene (30a) with the ligands 94a—e and 95 by Reiser and Glos.!“4] Scheme 14. Synthesis of new aza-bis(oxazoline) ligands 93a, b and 94a—c and the immobilization of 93b by Reiser and Glos. Table 15. Asymmetric cyclopropanation reaction! of styrene (30a) by Reiser and Glos.!“!
Figure 21. Monomer and polymer-supported pybox ligands 98a, b and poly-98a,b (Table 17) synthesized by Mayoral et a], [100]
Figure 21. Monomer and polymer-supported pybox ligands 98a, b and poly-98a,b (Table 17) synthesized by Mayoral et a], [100]
Table 16. Asymmetric cyclopropanation reaction"! of 97 and 73 by Glos and Reiser.|**! lal All reactions were carried out under nitrogen. >] Determined by HPLC using a Chiralpak AD column. (] Entry taken from ref.!°*!
Table 16. Asymmetric cyclopropanation reaction"! of 97 and 73 by Glos and Reiser.|**! lal All reactions were carried out under nitrogen. >] Determined by HPLC using a Chiralpak AD column. (] Entry taken from ref.!°*!
Table 17. Polymerization conditions!! used by Mayoral et al.!1°!
Table 17. Polymerization conditions!! used by Mayoral et al.!1°!
Table 19. Cyclopropanation reaction of substituted styrenes with ethyl diazoacetate catalyzed by dendritic ruthenium(II porphyrin 31-[G — 2], by Che et al.!®7]
Table 19. Cyclopropanation reaction of substituted styrenes with ethyl diazoacetate catalyzed by dendritic ruthenium(II porphyrin 31-[G — 2], by Che et al.!®7]
Scheme 16. Immobilization of dirhodium complexes 100 onto polymer-supported pyridines 103 by Davies and Nagashi- ma 104.107]
Scheme 16. Immobilization of dirhodium complexes 100 onto polymer-supported pyridines 103 by Davies and Nagashi- ma 104.107]
Table 20. Asymmetric cyclopropanation reaction of styrene (30a) with phenyldiazoacetate 104 using polymer-supported dirhodium catalysts 103 by Davies and Nagashima.!!%!07]
Table 20. Asymmetric cyclopropanation reaction of styrene (30a) with phenyldiazoacetate 104 using polymer-supported dirhodium catalysts 103 by Davies and Nagashima.!!%!07]
Scheme 17. Dirhodium complexes on pyridine-free solid support 106 by Davies and Nagashima.!%107]
Scheme 17. Dirhodium complexes on pyridine-free solid support 106 by Davies and Nagashima.!%107]
Figure 23. C,-Symmetrical phosphine ligands 109-111 on polymeric support by Stille et al.!7) Scheme 18. Hydroformylation of olefins.“")
Figure 23. C,-Symmetrical phosphine ligands 109-111 on polymeric support by Stille et al.!7) Scheme 18. Hydroformylation of olefins.“")
Figure 25. (25,4S)-N-(tert-Butoxycarbonyl)-4-(diphenylphos- phino)-2-[(diphenylphosphino)-methyl|pyrrolidine [(—)-BPPM] (113) cross-linked with polystyrene reported by Stille et al.) Figure 24. Polymer-bound chiral platinum complexes 112a,b by Stille et al.)
Figure 25. (25,4S)-N-(tert-Butoxycarbonyl)-4-(diphenylphos- phino)-2-[(diphenylphosphino)-methyl|pyrrolidine [(—)-BPPM] (113) cross-linked with polystyrene reported by Stille et al.) Figure 24. Polymer-bound chiral platinum complexes 112a,b by Stille et al.)
Table 23. Asymmetric hydroformylation reactions with different olefins using immobilized catalysts poly-115a by Nozak et al. [17]
Table 23. Asymmetric hydroformylation reactions with different olefins using immobilized catalysts poly-115a by Nozak et al. [17]
Table 22. Asymmetric hydroformylation reaction!) of styr- ene catalyzed by polymer-supported (R,S)-BINAPHOS derivatives poly-114 by Nozaki, Hiyama et al.!!!>]
Table 22. Asymmetric hydroformylation reaction!) of styr- ene catalyzed by polymer-supported (R,S)-BINAPHOS derivatives poly-114 by Nozaki, Hiyama et al.!!!>]
Figure 26. Phosphine-phosphane ligands 114a—d by Nozaki, Hiyama et al. 11516]
Figure 26. Phosphine-phosphane ligands 114a—d by Nozaki, Hiyama et al. 11516]
Figure 27. Catalyst [poly-115a-Rh(acac)] for the vapor-phase catalysis by Nozaki et al."
Figure 27. Catalyst [poly-115a-Rh(acac)] for the vapor-phase catalysis by Nozaki et al."
Table 24. Hydroformylation reactions using catalysts 116 by Nozaki et al.!"!8)
Table 24. Hydroformylation reactions using catalysts 116 by Nozaki et al.!"!8)
Scheme 19. Classical and asymmetric aldol reactions.!4)
Scheme 19. Classical and asymmetric aldol reactions.!4)
Scheme 20. Three-step synthesis of the resin-bound Evans’ oxazolidinone 123 by Abell et al.!"27]
Scheme 20. Three-step synthesis of the resin-bound Evans’ oxazolidinone 123 by Abell et al.!"27]
Scheme 23. Asymmetric aldol reaction catalyzed by BINAP complexes 128 and 129 by Fujii and Sodeoka.!!”*! Scheme 22. Conjugated addition on a resin-supported Evans’ auxiliary.!!77]
Scheme 23. Asymmetric aldol reaction catalyzed by BINAP complexes 128 and 129 by Fujii and Sodeoka.!!”*! Scheme 22. Conjugated addition on a resin-supported Evans’ auxiliary.!!77]
Scheme 21. Resin-supported asymmetric aldol reaction by Abell et al.!27]
Scheme 21. Resin-supported asymmetric aldol reaction by Abell et al.!27]
Scheme 24. Immobilization of proline ligand 133 by Cozzi et al. 192]
Scheme 24. Immobilization of proline ligand 133 by Cozzi et al. 192]
Scheme 25. Asymmetric aldol reaction catalyzed by immobi- lized proline catalyst 133 reported by Cozzi et al.!°7]
Scheme 25. Asymmetric aldol reaction catalyzed by immobi- lized proline catalyst 133 reported by Cozzi et al.!°7]
Table 27. Enantioselective synthesis of }-hydroxyketones 135a-d catalyzed by polymer-supported proline derivatives 137 and 138 bv Cozzi et al.!!3]
Table 27. Enantioselective synthesis of }-hydroxyketones 135a-d catalyzed by polymer-supported proline derivatives 137 and 138 bv Cozzi et al.!!3]
Scheme 26. Mukaiyama aldol reaction catalyzed by solid- supported bis(oxazoline) 6x by Salvadori et al./*)
Scheme 26. Mukaiyama aldol reaction catalyzed by solid- supported bis(oxazoline) 6x by Salvadori et al./*)
Figure 29. Polymer-supported La-BINOL catalyst poly-145a,b for asymmetric Michael addition reactions by Shibasaki et al.?*
Figure 29. Polymer-supported La-BINOL catalyst poly-145a,b for asymmetric Michael addition reactions by Shibasaki et al.?*
Table 30. Asymmetric Michael addition reaction by Shibasaki et al.!*«]
Table 30. Asymmetric Michael addition reaction by Shibasaki et al.!*«]
Scheme 27. Immobilized BINOL ligands 150 by Sasai et al.?7! 2] 145a: homogeneous La-linked BINOL; poly-145a: Polymer-supported La-linked BINOL; poly-145b: Polymer-supportec La-Zn-linked BINOL. [b] Ref [143]
Scheme 27. Immobilized BINOL ligands 150 by Sasai et al.?7! 2] 145a: homogeneous La-linked BINOL; poly-145a: Polymer-supported La-linked BINOL; poly-145b: Polymer-supportec La-Zn-linked BINOL. [b] Ref [143]
Scheme 29. Asymmetric conjugate addition reaction cata- lyzed by solid-supported phosphoramidate ligand 159 by Waldmann et al.!!*°! Scheme 28. Asymmetric Michael reaction catalyzed by the aluminium-containing catalyst 156 of Sundararajan and Prabagaran (in all cases the ratio, [Al]/[Michael acceptor] was kept at 0.5).!!“4l
Scheme 29. Asymmetric conjugate addition reaction cata- lyzed by solid-supported phosphoramidate ligand 159 by Waldmann et al.!!*°! Scheme 28. Asymmetric Michael reaction catalyzed by the aluminium-containing catalyst 156 of Sundararajan and Prabagaran (in all cases the ratio, [Al]/[Michael acceptor] was kept at 0.5).!!“4l
Scheme 30. Enantioselective addition of diethylzinc to ben- zaldehyde (124a).!!47] One of the best, if not the most, studied asymmetric C—C bond formation reaction in the liquid phase is the reaction of dialkylzinc reagents, particularly diethylzinc, with aldehydes.
Scheme 30. Enantioselective addition of diethylzinc to ben- zaldehyde (124a).!!47] One of the best, if not the most, studied asymmetric C—C bond formation reaction in the liquid phase is the reaction of dialkylzinc reagents, particularly diethylzinc, with aldehydes.
Table 31. Asymmetric addition of dialkylzinc derivatives to aldehydes!! by Soai et al.!!“*!
Table 31. Asymmetric addition of dialkylzinc derivatives to aldehydes!! by Soai et al.!!“*!
Scheme 31. Synthesis of ephedrine 11a and the derivatives 11b,c by Soai et al.!”!
Scheme 31. Synthesis of ephedrine 11a and the derivatives 11b,c by Soai et al.!”!
Figure 32. Polymer-bound N-methyl-norephedrine 162a as a chiral catalyst.!!*8)
Figure 32. Polymer-bound N-methyl-norephedrine 162a as a chiral catalyst.!!*8)
Scheme 32. Synthesis of polymer-bound ephedrine catalysts 162a—c by Soai et al."
Scheme 32. Synthesis of polymer-bound ephedrine catalysts 162a—c by Soai et al."
Figure 33. First polymer-supported TADDOL-system 164,!! styryl-substituted TADDOL derivatives 3b—e for copolymeriza- tion}! and TADDOL ligand 165 immobilized on hydrophobic controlled-pore-glass silica gel by Seebach et al.!"*) The immobilization of a TADDOL ligand was also performed on hydrophobic controlled-pore glass (CPG) silica gel (165) (Figure 33).!'! After loading with Ti(O- i-Pr),, the corresponding ligand was tested in the addition of diethylzinc on benzaldehyde (124a) giving rise to a 95% yield and <98% ee. The immobilized chiral catalysts were used 20 times with only minor loss of selectivity. After 20 cycles the catalyst were washed with HCl, H,O, and acetone, then reloaded with the titanate source and used again. It is remarkable that the same selectivity was observed as for the first run. These examples demonstrate that there is only a slight leaching of the center metal. Polymer-bound catalysts with low loading (0.1 mmol TADDOL/g polymer) gave the best rates. The enantio- selectivity was always better than 80% ee. Quite re- markable is the fact that only the dendritic polymer makes over 20 cycles with a constant enantiomeric excess of 96% ee. The efficiency of the catalyst decreas- es if the length of the not branched chain is longer
Figure 33. First polymer-supported TADDOL-system 164,!! styryl-substituted TADDOL derivatives 3b—e for copolymeriza- tion}! and TADDOL ligand 165 immobilized on hydrophobic controlled-pore-glass silica gel by Seebach et al.!"*) The immobilization of a TADDOL ligand was also performed on hydrophobic controlled-pore glass (CPG) silica gel (165) (Figure 33).!'! After loading with Ti(O- i-Pr),, the corresponding ligand was tested in the addition of diethylzinc on benzaldehyde (124a) giving rise to a 95% yield and <98% ee. The immobilized chiral catalysts were used 20 times with only minor loss of selectivity. After 20 cycles the catalyst were washed with HCl, H,O, and acetone, then reloaded with the titanate source and used again. It is remarkable that the same selectivity was observed as for the first run. These examples demonstrate that there is only a slight leaching of the center metal. Polymer-bound catalysts with low loading (0.1 mmol TADDOL/g polymer) gave the best rates. The enantio- selectivity was always better than 80% ee. Quite re- markable is the fact that only the dendritic polymer makes over 20 cycles with a constant enantiomeric excess of 96% ee. The efficiency of the catalyst decreas- es if the length of the not branched chain is longer
Table 33. Addition of Et,Zn to PhCHO (124a) catalyzed!! by solid-supported BINOLs poly-le-h reported by Seebach et al.!41
Table 33. Addition of Et,Zn to PhCHO (124a) catalyzed!! by solid-supported BINOLs poly-le-h reported by Seebach et al.!41
Scheme 33. Synthesis of modified BINOL derivatives 1a, ¢, d used for the preparation of polymeric catalyst by Seebach et al.!4) Table 32. Addition of Et,Zn to PhCHO (124a) catalyzed!*! by soluble BINOLs 1e-h by Seebach et al.!“)
Scheme 33. Synthesis of modified BINOL derivatives 1a, ¢, d used for the preparation of polymeric catalyst by Seebach et al.!4) Table 32. Addition of Et,Zn to PhCHO (124a) catalyzed!*! by soluble BINOLs 1e-h by Seebach et al.!“)
Scheme 34. Multiple use of polymer-bound BINOLate poly- le-h by Seebach et al.!4!
Scheme 34. Multiple use of polymer-bound BINOLate poly- le-h by Seebach et al.!4!
The reactions are completed within 12—16 hours for aromatic aldehydes and 3-4 days for aliphatic alde- hydes.
The reactions are completed within 12—16 hours for aromatic aldehydes and 3-4 days for aliphatic alde- hydes.
Table 34. Addition of diethylzinc to aldehydes!! with catalyst 1j reported by Pu et al.
Table 34. Addition of diethylzinc to aldehydes!! with catalyst 1j reported by Pu et al.
Figure 36. Sterically regular chiral polybinaphthol 54, and the soluble dendrimer 1k based on BINOL by Pu et al.°-53!
Figure 36. Sterically regular chiral polybinaphthol 54, and the soluble dendrimer 1k based on BINOL by Pu et al.°-53!
Figure 38. Polymer-bound 1-aryl-3-alkyltriazenes by Brase, Leadbeater et al.!'*5!
Figure 38. Polymer-bound 1-aryl-3-alkyltriazenes by Brase, Leadbeater et al.!'*5!
Scheme 35. Activity of the polymer triazenes and metal complexes used by Brase, Leadbeater et al.!!°°)
Scheme 35. Activity of the polymer triazenes and metal complexes used by Brase, Leadbeater et al.!!°°)
Table 35. Enantioselective ethylation of imines with dialkyl- zinc by Soai et al.[°¢
Table 35. Enantioselective ethylation of imines with dialkyl- zinc by Soai et al.[°¢
Figure 42. Polymer-supported prolinol catalysts 174a, b intro- duced for asymmetric diethylzinc addition reactions to aldehydes by Hodge et al.!1*! Figure 41. Polymer-anchored chiral amino oxazolines 173a,b introduced by Bedekar et al.!'**!
Figure 42. Polymer-supported prolinol catalysts 174a, b intro- duced for asymmetric diethylzinc addition reactions to aldehydes by Hodge et al.!1*! Figure 41. Polymer-anchored chiral amino oxazolines 173a,b introduced by Bedekar et al.!'**!
Figure 43. Immobilized ferrocenyl ligands 175a,b reported by Bolm et al. benzaldehyde (124a) and good enantioselectivities (ee up to 95%) were obtained in addition reactions of diethylzinc to different aromatic aldehydes.
Figure 43. Immobilized ferrocenyl ligands 175a,b reported by Bolm et al. benzaldehyde (124a) and good enantioselectivities (ee up to 95%) were obtained in addition reactions of diethylzinc to different aromatic aldehydes.
Figure 44. Immobilized amino alcohols 176a—c by Martens et al, [61] aldehydes (Figure 43)"! causing excellent enantiose- lectivities (up to 97% ee) which decreased after recy- cling (four times) only very slightly.
Figure 44. Immobilized amino alcohols 176a—c by Martens et al, [61] aldehydes (Figure 43)"! causing excellent enantiose- lectivities (up to 97% ee) which decreased after recy- cling (four times) only very slightly.
Table 37. Enantioselective Reissert-type reaction using homogeneous 18la and solid-supported catalyst 181b by Shibasaki et al.
Table 37. Enantioselective Reissert-type reaction using homogeneous 18la and solid-supported catalyst 181b by Shibasaki et al.
Table 36. Enantioselective Strecker reaction catalyzed by 181¢ by Shibasaki et al.)
Table 36. Enantioselective Strecker reaction catalyzed by 181¢ by Shibasaki et al.)
Scheme 39. Enantioselective Reissert-type reaction by Shi- basaki et al.!!4] Scheme 38. Enantioselective Strecker type reaction with polymer-supported bifunctional catalyst 181¢.!'!
Scheme 39. Enantioselective Reissert-type reaction by Shi- basaki et al.!!4] Scheme 38. Enantioselective Strecker type reaction with polymer-supported bifunctional catalyst 181¢.!'!
Scheme 37. The concept for the immobilization of the tridentate Schiff base ligands 176 and asymmetric Strecker type reaction with immobilized Schiff base ligands poly-176 by Jacobsen et al.!!@!
Scheme 37. The concept for the immobilization of the tridentate Schiff base ligands 176 and asymmetric Strecker type reaction with immobilized Schiff base ligands poly-176 by Jacobsen et al.!!@!
Scheme 41. Asymmetric Mannich-type reaction with solid- supported BINAP ligand 128 by Sodeoka et al.!!8) Scheme 40. Classical Mannich reaction and asymmetric Man- nich-type reaction.
Scheme 41. Asymmetric Mannich-type reaction with solid- supported BINAP ligand 128 by Sodeoka et al.!!8) Scheme 40. Classical Mannich reaction and asymmetric Man- nich-type reaction.
Figure 45. Cu-BOX complexes 6a by Evans et al.!!°7 and 6c by Evans et al.!!°)
Figure 45. Cu-BOX complexes 6a by Evans et al.!!°7 and 6c by Evans et al.!!°)
Scheme 43. Hetero ituti . geneous substitution of i by Lemaire, Fache et al." anynS BREE Scheme 42. Immobilized BINOL ligands 150 by Sasai et al.?”1 and asymmetric carbonyl ene reaction catalyzed by polymer- supported Ti-BINOL complexes 194a-c by Ikegami et al.!'©°! The group of Lemaire, Fache et al. presen ed a solid- supported C,-symmetric chiral nitrogen ligand 197 for this useful reaction.” pure diamine with a Treatment of a chiral, enantio- diisocyanate or with a diacid chloride resulted in polyaddition or polycondensation reaction to give insolu After reaction of both polymeric cata ble poly(ureas) or po y(amides). lysts with [PdCl(7?-C3H;)], asymmetric allylic substitution reac- tions of allylic aceta es with malonates have been performed (Scheme 43). The results are presented in Table 39. There is no possibility to reuse the heteroge- neous catalyst. After tates on the polymer he reaction, palladium precipi- causing a black color with the catalyst loosing its activity. Both polymeric catalysts are also less reactive than he homogeneous one
Scheme 43. Hetero ituti . geneous substitution of i by Lemaire, Fache et al." anynS BREE Scheme 42. Immobilized BINOL ligands 150 by Sasai et al.?”1 and asymmetric carbonyl ene reaction catalyzed by polymer- supported Ti-BINOL complexes 194a-c by Ikegami et al.!'©°! The group of Lemaire, Fache et al. presen ed a solid- supported C,-symmetric chiral nitrogen ligand 197 for this useful reaction.” pure diamine with a Treatment of a chiral, enantio- diisocyanate or with a diacid chloride resulted in polyaddition or polycondensation reaction to give insolu After reaction of both polymeric cata ble poly(ureas) or po y(amides). lysts with [PdCl(7?-C3H;)], asymmetric allylic substitution reac- tions of allylic aceta es with malonates have been performed (Scheme 43). The results are presented in Table 39. There is no possibility to reuse the heteroge- neous catalyst. After tates on the polymer he reaction, palladium precipi- causing a black color with the catalyst loosing its activity. Both polymeric catalysts are also less reactive than he homogeneous one
Table 39. Asymmetric allylic substitution by Lemaire, Fache et all
Table 39. Asymmetric allylic substitution by Lemaire, Fache et all
Table 40. Asymmetric allylic substitution! by Hayashi and Uozumi.0 '] Conditions: 1 equiv. 201, 1 equiv. 202, base, catalyst.
Table 40. Asymmetric allylic substitution! by Hayashi and Uozumi.0 '] Conditions: 1 equiv. 201, 1 equiv. 202, base, catalyst.
Figure 46. Resin-supported MOP ligands (PEG-MOP 200a-f by Hayashi and Uozumi.!!”)
Figure 46. Resin-supported MOP ligands (PEG-MOP 200a-f by Hayashi and Uozumi.!!”)
Scheme 45. Synthesis of helical sense selective polymers poly-206 by polymerization of methacrylates 204a,b with the additives 205a and (S)-(+)-205b by Reggelin et al.!'72]
Scheme 45. Synthesis of helical sense selective polymers poly-206 by polymerization of methacrylates 204a,b with the additives 205a and (S)-(+)-205b by Reggelin et al.!'72]
Scheme 47. Asymmetric hetero Diels—Alder reaction with a solid-supported BINOL ligand 11 by Pu et al.°791
Scheme 47. Asymmetric hetero Diels—Alder reaction with a solid-supported BINOL ligand 11 by Pu et al.°791
Scheme 48. Optimized soluble zirconium-binaphthol catalyst 221 for Diels-Alder reactions and aza-Diels—Alder reaction catalyzed by polymer-supported zirconium-binaphthol cata- lyst 219 by Kobayashi et al. (Table 41).(?34185]
Scheme 48. Optimized soluble zirconium-binaphthol catalyst 221 for Diels-Alder reactions and aza-Diels—Alder reaction catalyzed by polymer-supported zirconium-binaphthol cata- lyst 219 by Kobayashi et al. (Table 41).(?34185]
Scheme 46. Diels-Alder reaction with endo transition state!!”] and homogeneous chiral catalysts for Diels-Alder reactions. !!78-180]
Scheme 46. Diels-Alder reaction with endo transition state!!”] and homogeneous chiral catalysts for Diels-Alder reactions. !!78-180]
Table 41. Catalyst optimization of polymer-supported zirco- nium-binaphthol catalyst 219 in the aza-Diels—Alder reac- tion! by Kobayashi et al. (Scheme 48) 174]
Table 41. Catalyst optimization of polymer-supported zirco- nium-binaphthol catalyst 219 in the aza-Diels—Alder reac- tion! by Kobayashi et al. (Scheme 48) 174]
Scheme 49. Hetero-Diels—Alder reaction catalyzed (non) dendritic using Cr-salen complexes poly-8e, poly-20e and poly-22a- Cr(X) by Seebach et al. (Table 42).!* In the same year, Hyeon and Kim et al. immobilized a copper-chiral bis(oxazoline) complex on mesoporous silica and employed it as catalyst 224 in a Diels-Alder reaction (Scheme 50). !"8¢!
Scheme 49. Hetero-Diels—Alder reaction catalyzed (non) dendritic using Cr-salen complexes poly-8e, poly-20e and poly-22a- Cr(X) by Seebach et al. (Table 42).!* In the same year, Hyeon and Kim et al. immobilized a copper-chiral bis(oxazoline) complex on mesoporous silica and employed it as catalyst 224 in a Diels-Alder reaction (Scheme 50). !"8¢!
Scheme 50. Diels— Alder reaction catalyzed by silica-indabox 224 by Hyeon and Kim et al_!!°¢1
Scheme 50. Diels— Alder reaction catalyzed by silica-indabox 224 by Hyeon and Kim et al_!!°¢1
able 42. Hetero-Diels—Alder reaction! (Scheme 49) by Seebach et al.!! The enantioselectivities obtained with simple nsubstituted Cr(Cl)-salen are the following: 222a 60% ee; 222b 78% ee; 222c 74% ee. ] Conditions: 1 equiv. 218, 1 equiv. 124a, d, g, 0.02 equiv. poly-8e-, poly-20¢ or poly-22a-Cr(X), MeO-t-Bu, rt, 24h (X=Cl, F, BF,).
able 42. Hetero-Diels—Alder reaction! (Scheme 49) by Seebach et al.!! The enantioselectivities obtained with simple nsubstituted Cr(Cl)-salen are the following: 222a 60% ee; 222b 78% ee; 222c 74% ee. ] Conditions: 1 equiv. 218, 1 equiv. 124a, d, g, 0.02 equiv. poly-8e-, poly-20¢ or poly-22a-Cr(X), MeO-t-Bu, rt, 24h (X=Cl, F, BF,).
Table 43. Asymmetric Diels-Alder reaction between cyclopentadiene 207a and acrylamide 223a using 10 mol% of 224 by Hyeon and Kim et al. (Scheme 50).!!°¢!
Table 43. Asymmetric Diels-Alder reaction between cyclopentadiene 207a and acrylamide 223a using 10 mol% of 224 by Hyeon and Kim et al. (Scheme 50).!!°¢!
Scheme 52. Immobilization of bis(oxazoline) ligand 6d by polymerization as part of the main chain of a polyurethane backbone 227 (route A) and by grafting onto a silica surface 228a (route B) by Lemaire et al.!* The catalyst 228a grafted on silica gave 87% ee at — 78°C (entry 1, Table 45). Even at higher temperature it gave better enantioselectivities than the polymer- supported catalyst 227. The enantioselectivity de- Scheme 51. Enantioselective Diels-Alder reaction by Mo- berg et al.!°5! and Cozzi et al.8)
Scheme 52. Immobilization of bis(oxazoline) ligand 6d by polymerization as part of the main chain of a polyurethane backbone 227 (route A) and by grafting onto a silica surface 228a (route B) by Lemaire et al.!* The catalyst 228a grafted on silica gave 87% ee at — 78°C (entry 1, Table 45). Even at higher temperature it gave better enantioselectivities than the polymer- supported catalyst 227. The enantioselectivity de- Scheme 51. Enantioselective Diels-Alder reaction by Mo- berg et al.!°5! and Cozzi et al.8)
Scheme 53. Enantioselective Diels-Alder reactions with a metal-free polymer-supported ligand 231a and 231b by Cozzi et al, {190 observed was 92% ee for the endo product at a reaction temperature of — 78°C (quantitative conversion). Fur- thermore, the authors introduced other substrates in the Diels—Alder reaction catalyzed by the silica-supported ligand 228a with enantioselectivities only somewhat lower compared with the homogeneous catalyst.
Scheme 53. Enantioselective Diels-Alder reactions with a metal-free polymer-supported ligand 231a and 231b by Cozzi et al, {190 observed was 92% ee for the endo product at a reaction temperature of — 78°C (quantitative conversion). Fur- thermore, the authors introduced other substrates in the Diels—Alder reaction catalyzed by the silica-supported ligand 228a with enantioselectivities only somewhat lower compared with the homogeneous catalyst.
Scheme 54. Enantioselective hetero-Diels—Alder reactions with the silica gel-supported Cr-salen catalyst 8b by Seebach et al. and soluble Cr-salen complex 8¢.!°°! The selectivities obtained with poly-1m - AlMe corre- spond to those found in homogeneous solution.!'%! There seems to be no dependence of performance of
Scheme 54. Enantioselective hetero-Diels—Alder reactions with the silica gel-supported Cr-salen catalyst 8b by Seebach et al. and soluble Cr-salen complex 8¢.!°°! The selectivities obtained with poly-1m - AlMe corre- spond to those found in homogeneous solution.!'%! There seems to be no dependence of performance of
Scheme 55. Enantioselective Diels-Alder reactions catalyzed by JandaJel™-bound amine catalyst 236 and silica-supported amine catalyst 237 by Pihko et al.!'7! Scheme 56. 1,3-Dipolar cycloaddition reactions catalyzed by poly-1m (substituted BINOL Im as precursor for the solid- supported ligand poly-1m) by Seebach et al.!4]
Scheme 55. Enantioselective Diels-Alder reactions catalyzed by JandaJel™-bound amine catalyst 236 and silica-supported amine catalyst 237 by Pihko et al.!'7! Scheme 56. 1,3-Dipolar cycloaddition reactions catalyzed by poly-1m (substituted BINOL Im as precursor for the solid- supported ligand poly-1m) by Seebach et al.!4]
Very recently, Seebach et al. reported on the applica- ion of polymerization of TADDOL 3b and its applica- ion in a 1,3-dipolar cycloaddition reaction of diphenyl- nitrone (238 to [(£)-but-2-enoyl]-oxazolidinone (223b) Scheme 57).!°! The polymer poly-3b was loaded with itanate by the addition of a solution of TiCl,(O-i-Pr), or Ti(OTs),(O-i-Pr). Conversion (93%), endolexo selec- ivity (82:18) and enantioselectivity (exo 75% ee) by using poly-3b-TiCl, were comparable with those ob- ained in solution phase.!'*”! It turned out that high conversions could only be achieved when 50 mol % of poly-3b were used, whereas the reaction in solution proceeded well in the presence of 10 mol % catalyst. Recycling of poly-3b also proved successful. The preferential formation of exo-cycloadduct exo-241 is
Very recently, Seebach et al. reported on the applica- ion of polymerization of TADDOL 3b and its applica- ion in a 1,3-dipolar cycloaddition reaction of diphenyl- nitrone (238 to [(£)-but-2-enoyl]-oxazolidinone (223b) Scheme 57).!°! The polymer poly-3b was loaded with itanate by the addition of a solution of TiCl,(O-i-Pr), or Ti(OTs),(O-i-Pr). Conversion (93%), endolexo selec- ivity (82:18) and enantioselectivity (exo 75% ee) by using poly-3b-TiCl, were comparable with those ob- ained in solution phase.!'*”! It turned out that high conversions could only be achieved when 50 mol % of poly-3b were used, whereas the reaction in solution proceeded well in the presence of 10 mol % catalyst. Recycling of poly-3b also proved successful. The preferential formation of exo-cycloadduct exo-241 is
Table 48. Enantioselective Diels-Alder reaction catalyzed by JandaJel™-bound amine 235 by Pihko et al.!' 'al Calculated based on the amine loading (mmol/g) of the supported catalyst. The loading is based on the original nitroget loading of the support but a correction has been made for the mass gain of the catalyst during its preparation. endo:exo ratios were determined by 'H NMR from the aldehyde product mixture. For determination of the ee values, th aldehyde products were first reduced to the alcohols with excess of NaBH, in EtOH, and the resulting alcohols were ar analyzed by GLC using Supelco y-DEX™ 120 column. Absolute and relative configuration were assigned by chemica correlation to compounds obtained by known solution phase methods"! or by analogy. (cl Yields of isolated, purified aldehydes. [4] Reaction was nerformed with catalvst recovered from previous run. [b]
Table 48. Enantioselective Diels-Alder reaction catalyzed by JandaJel™-bound amine 235 by Pihko et al.!' 'al Calculated based on the amine loading (mmol/g) of the supported catalyst. The loading is based on the original nitroget loading of the support but a correction has been made for the mass gain of the catalyst during its preparation. endo:exo ratios were determined by 'H NMR from the aldehyde product mixture. For determination of the ee values, th aldehyde products were first reduced to the alcohols with excess of NaBH, in EtOH, and the resulting alcohols were ar analyzed by GLC using Supelco y-DEX™ 120 column. Absolute and relative configuration were assigned by chemica correlation to compounds obtained by known solution phase methods"! or by analogy. (cl Yields of isolated, purified aldehydes. [4] Reaction was nerformed with catalvst recovered from previous run. [b]
Scheme 58. Olefin metathesis reaction.!'%"!
Scheme 58. Olefin metathesis reaction.!'%"!
Scheme 57. 1,3-Dipolar cycloaddition reactions catalyzed by poly-3b by Seebach et al.!6 are still under improvement in terms of efficiency, turnover frequencies, long-term stability and tolerance toward functional groups. However, the state of the art provides the chemical community with highly active and nevertheless bench stable catalysts. In Figure 47 are shown three important metathesis catalysts.!19?!
Scheme 57. 1,3-Dipolar cycloaddition reactions catalyzed by poly-3b by Seebach et al.!6 are still under improvement in terms of efficiency, turnover frequencies, long-term stability and tolerance toward functional groups. However, the state of the art provides the chemical community with highly active and nevertheless bench stable catalysts. In Figure 47 are shown three important metathesis catalysts.!19?!
Figure 48. Some chiral metathesis catalysts 245-247!" and first polymer-supported chiral catalyst 248 for asymmetric olefin metathesis reactions by Schrock, Hoveyda et al.!'°!
Figure 48. Some chiral metathesis catalysts 245-247!" and first polymer-supported chiral catalyst 248 for asymmetric olefin metathesis reactions by Schrock, Hoveyda et al.!'°!
Scheme 59. Asymmetric olefin metathesis reaction catalyzed by immobilized 248 by Schrock, Hoveyda et al.!7!°l
Scheme 59. Asymmetric olefin metathesis reaction catalyzed by immobilized 248 by Schrock, Hoveyda et al.!7!°l
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