SCREEIG OF,-BIDETATE PYRIDIE-BASED LIGADS I COPPER AD PALLADIUM CATALYSED REACTIOS MAURIZIO SOLIAS
ITRO: Green Chemistry Principle #9 Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. "CAT" CAT is a substance that changes the velocity of a reaction without itself being changed in the process. It can be used in small amounts and be recycled indefinitely (at lest in principle) Doesn t generate any waste. Catalysis is nowadays wide applied in petrochemical industry, in the pharmaceutical and fine chemical industries. All types of catalysis are generally applied in modern chemistry: heterogeneous, homogeneous, organocatalysts and, ature s own exquisite catalysts: enzymes.
OMOGEEOUS REACTIOS: In homogeneous catalysis the reactants, products and catalyst are all in the same phase. Often the reactants, products and catalyst are all dissolved in the same solvent. A narrower definition has become fashionable according to which homogeneous catalysis involves (organo)metallic complexes as the catalyst. ot every homogenous catalytic process contains an organometallic metal complexes : - acid and base catalysis (ester hydrolysis), - Lewis acids as catalysts (Diels-Alder reactions), - organic catalysts (thiazolium ions in Cannizzarro reactions), - porphyrin complexes (epoxidations, hydroxylations), - enzymatic processes, - co-ordination complexes (polyester condensations). Ligand effects are extremely important in homogeneous catalysis by metal complexes. One metal can give a variety of products from one single substrate simply by changing the ligands around the metal centre. Chemoselectivity Regioselectivity - Diastereoselectivity Enantioselectivity
The ligands 1/2 1 2 3 4 5 6 7 8 9 10
The ligands 2/2 11 12 13 14 15 16 17 18 19 20
Enantioselective Copper(II)-Catalyzed enry Reaction Ligand Conversion, % B-Yield, % C-Yield, % e.e., % conf. 1 86 30 56 41 S 2 100 67 33 33 S 3 80 58 22 17 R 4 83 59 24 22 S 5 62 41 21 66 R 6 75 10 65 0 -- 7 92 32 60 45 R 8 88 78 10 13 R 9 73 66 7 31 S 10 46 26 20 4 S 5 (0 C) 100 90 10 79 R 5 (-30 C) 63 55 8 82 R 5(-30 C, 48h) 95 79 16 81 R M. Solinas, B. Sechi, S. Baldino, G. Chelucci, J. Mol. Catal. A: Chemical 378 (2013) 206 212
Enantioselective Copper(II)-Catalyzed enry Reaction Ligand Conversion, % B-Yield, % C-Yield, % e.e., % conf. 1 86 30 56 41 S 2 100 67 33 33 S 3 80 58 22 17 R 4 83 59 24 22 S 5 62 41 21 66 R 6 75 10 65 0 -- 7 92 32 60 45 R 8 88 78 10 13 R 9 73 66 7 31 S 10 46 26 20 4 S 5 (0 C) 100 90 10 79 R 5 (-30 C) 63 55 8 82 R 5(-30 C, 48h) 95 79 16 81 R 5 6 1 2 3 7 R 8-10 4 M. Solinas, B. Sechi, S. Baldino, G. Chelucci, J. Mol. Catal. A: Chemical 378 (2013) 206 212
Palladium-catalysed asymmetric allylic alkylation Ligand Time, h Conversion, % Yield, % e.e., % conf. 11 20 100 91 54 S 12 20 100 92 38 S 13 72 62 23 62 S 14 72 50 30 20 R 15 24 100 88 34 R 16 44 95 89 16 S 17 21 100 95 20 S 18 72 70 63 18 R 19 24 87 87 16 S 20 72 44 35 9 S 1 20 100 92 7 R 4 20 100 98 25 S 5 24 100 87 0 -- M. Solinas, B. Sechi, G. Chelucci, S. Baldino, J. R. Pedro, G. Blay, J. Mol. Catal. A: Chemical 385 (2014) 73 77
Palladium-catalysed asymmetric allylic alkylation Ligand Time, h Conversion, % Yield, % e.e., % conf. 11 20 100 91 54 S 12 20 100 92 38 S 13 72 62 23 62 S 14 72 50 30 20 R 15 24 100 88 34 R 16 44 95 89 16 S 17 21 100 95 20 S 18 72 70 63 18 R 19 24 87 87 16 S 20 72 44 35 9 S 1 20 100 92 7 R 4 20 100 98 25 S 5 24 100 87 0 -- 1 4 5 M. Solinas, B. Sechi, G. Chelucci, S. Baldino, J. R. Pedro, G. Blay, J. Mol. Catal. A: Chemical 385 (2014) 73 77
Cu(I)-catalysed asymmetric allylic oxidation Ligand Time, h n Yield, % e.e., % conf. 21 48 1 51 6 R 22 48 1 23 5 R 23 120 1 30 3 R 24 96 1 52 0 -- 11 24 1 51 14 S 12 24 1 57 3 S 15 48 1 37 5 S 13 48 1 37 0 -- 14 24 1 63 51 S 14 24 0 70 40 S 14 24 2 44 53 S 14 24 3 24 34 S M. Solinas, B. Sechi, G. Chelucci Appl. Organometal. Chem. 2014, 28, 831 834
Cu(I)-catalysed asymmetric allylic oxidation Ligand Time, h n Yield, % e.e., % conf. 21 48 1 51 6 R 22 48 1 23 5 R 23 120 1 30 3 R 24 96 1 52 0 -- 11 24 1 51 14 S 12 24 1 57 3 S 15 48 1 37 5 S 13 48 1 37 0 -- 14 24 1 63 51 S 14 24 0 70 40 S 14 24 2 44 53 S 14 24 3 24 34 S O O S S 21 O O S S 22 23 24 M. Solinas, B. Sechi, G. Chelucci Appl. Organometal. Chem. 2014, 28, 831 834
Conclusions 1) For the enantioselective copper(ii)-catalyzed enry reaction ligand 5 gave the 1-(2-Methoxyphenyl)-2-nitroethanol in moderate yields and good enantioselectivities (up to 82% ee) under straightforward experimental conditions without the need for air or moisture exclusion. 2) For the enantioselective palladium catalyzed allylic substitution of 1,3- diphenylprop-2-enyl acetate with dimethyl malonate, the product dimethyl 1,3- diphenylprop-2-enylmalonate was produced in good yields and moderate enantioselectivities (up to 62% ee) by using ligand 13. 3) In the catalytic allylic oxidation of cyclic olefins the best yields (up to 70%) and enantioselectivities (up to 53% enantiomeric excess) were obtained with an iminopyridine based on camphane and quinoline skeletons (14).
Acknowledgements Giorgio Chelucci Barbara Sechi Salvatore Baldino José R. Pedro Gonzalo Blay Financial support : CR University of Sassari Regione Sardegna Fondazione Banco di Sardegna