Homogeneous and Supported Copper Complexes of Cyclic and Open-Chain Polynitrogenated Ligands as Catalysts of Cyclopropanation Reactions

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

“…8). 126 When the copper complexes of the homogeneous analogues 53 and 54 were evaluated for this reaction, the presence of an induction period was observed. No conversion of 50 to 52 was detected for a period of 1 to 3 hours.…”

Cu2+, Zn2+, and Ni2+ Complexes of C2-Symmetric Pseudopeptides with an Aromatic Central Spacer

“…Different metal complexes of pseudopeptidic ligands have shown to be catalytically active for a variety of organic transformations. ,,, In this regard, the ring-opening of epoxides with an amine as the nucleophile is an important, but challenging, route for the synthesis of β-amino alcohols. , Some of the existing methods have limitations, including the failure of less basic amines to open epoxides under ambient conditions, the requirement of high catalyst loading, the need of using air- and moisture-sensitive catalysts, nonenvironmentally friendly solvents, or long reaction times . Taking this into account and in order to obtain information on the potential catalytic activity of the considered metal complexes, preliminary studies were carried out on the use of the corresponding Cu 2+ , Zn 2+ , and Ni 2+ complexes with ligands 5 and 6 for the ring-opening of cyclohexene oxide with aniline using water and EtOH as environmentally friendly solvents (Scheme ).…”

“…In this context, symmetrical tetracoordinated Schiff base metal complexes derived from amino acids, containing aromatic central spacers, have been studied as catalysts for Et 2 Zn addition reactions and as chiral porphyrin mimics . Furthermore, recent contributions from our group have shown how minimalistic pseudopeptides derived from simple natural amino acids, with the general structures I–III (Chart ), can have important applications, and have been reported as chiral solvating agents or selective receptors for substrates of biological relevance, as minimalistic molecular machines, as organogelators, acting as “ in vivo ” fluorescent pH probes, and as ligands for the preparation of enantioselective catalysts …”

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“…Cationic exchange is a simple and efficient strategy, already used in the case of non-chiral catalysts [2][3][4]. For this purpose, clays [9][10][11][12][13][14] and nafion-type solids [14,15] have been used as supports. The covalent anchoring to insoluble supports has also been used as an immobilization strategy.…”

“…The covalent anchoring to insoluble supports has also been used as an immobilization strategy. In that case both organic polymers [11,[16][17][18][19] and inorganic solids [19][20][21][22][23][24] have shown their efficiency. Even the natural polymer chitosan has been used as a chiral support to form copper complexes active in cyclopropanation reactions [25].…”