We have recently reported that copper(I) complexes of the new C1-symmetric pyridine-based 12-membered tetraaza macrocycles, Pyridine Containing Ligands (Pc-L*), are competent catalysts in the asymmetric cyclopropanation.[1] We report here the synthesis of new C1- and C2-symmetric Pc-L* macrocycles and the use of their Cu(I) complexes as catalysts for the title reaction. The synthetic paths, reportedi in Scheme 1, are very simple and they take advantage of commercially available, enantiomerically pure, chiral amino-alcohols and/or primary amines. These last compounds can react either with 2,6-bis(chloromethyl)pyridine(path A) or with the stereochemically pure forms of the alkyl pyridines obtained by the Lipase-catalyzed kinetic acetylation of 2,6-bis(1-hydroxyethyl)pyridine [2] (path B). Ligands with different structures have been obtained in moderate to good yields (40-80%) and they have been fully characterized. The Cu(I) complexes of those ligands showed good catalytic activities in the cyclopropanation of differently substituted olefins employing ethyl diazoacetate (EDA) as carbene precursor. In all cases a complete conversion of EDA was observed and, depending on the employed ligand, cyclopropanes were obtained with tunable cis/trans stereoselectivities and e.e. up to 96%. [1] Caselli, A.; Cesana, F.; Gallo, E.; Casati, N.; Macchi, P.; Sisti, M.; Celentano, G.; Cenini, S. Dalton Trans. 2008, 4202-4205. [2] Uenishi, J.; Aburatani, S.; Takami, V. J. Org. Chem., 2007, 72, 132-138.

How structural modifications can tune the asymmetric cyclopropanations catalyzed by Cu(I) complexes of chiral pyridine containing macrocylcic ligands (Pc-L*) / B. Castano, E. Gallo, A. Caselli. ((Intervento presentato al 8. convegno International School of Organometallic Chemistry tenutosi a Camerino nel 2011.

How structural modifications can tune the asymmetric cyclopropanations catalyzed by Cu(I) complexes of chiral pyridine containing macrocylcic ligands (Pc-L*)

B. Castano
Primo
;
E. Gallo
Secondo
;
A. Caselli
Ultimo
2011-08

Abstract

We have recently reported that copper(I) complexes of the new C1-symmetric pyridine-based 12-membered tetraaza macrocycles, Pyridine Containing Ligands (Pc-L*), are competent catalysts in the asymmetric cyclopropanation.[1] We report here the synthesis of new C1- and C2-symmetric Pc-L* macrocycles and the use of their Cu(I) complexes as catalysts for the title reaction. The synthetic paths, reportedi in Scheme 1, are very simple and they take advantage of commercially available, enantiomerically pure, chiral amino-alcohols and/or primary amines. These last compounds can react either with 2,6-bis(chloromethyl)pyridine(path A) or with the stereochemically pure forms of the alkyl pyridines obtained by the Lipase-catalyzed kinetic acetylation of 2,6-bis(1-hydroxyethyl)pyridine [2] (path B). Ligands with different structures have been obtained in moderate to good yields (40-80%) and they have been fully characterized. The Cu(I) complexes of those ligands showed good catalytic activities in the cyclopropanation of differently substituted olefins employing ethyl diazoacetate (EDA) as carbene precursor. In all cases a complete conversion of EDA was observed and, depending on the employed ligand, cyclopropanes were obtained with tunable cis/trans stereoselectivities and e.e. up to 96%. [1] Caselli, A.; Cesana, F.; Gallo, E.; Casati, N.; Macchi, P.; Sisti, M.; Celentano, G.; Cenini, S. Dalton Trans. 2008, 4202-4205. [2] Uenishi, J.; Aburatani, S.; Takami, V. J. Org. Chem., 2007, 72, 132-138.
Settore CHIM/03 - Chimica Generale e Inorganica
How structural modifications can tune the asymmetric cyclopropanations catalyzed by Cu(I) complexes of chiral pyridine containing macrocylcic ligands (Pc-L*) / B. Castano, E. Gallo, A. Caselli. ((Intervento presentato al 8. convegno International School of Organometallic Chemistry tenutosi a Camerino nel 2011.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/166069
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