Zirconium Complexes Supported by Imidazolones: Synthesis, Characterization, and Application of Precatalysts for the Hydroamination of Aminoalkenes

The Highly Regioselective Synthesis of Novel Imidazolidin-2-Ones via the Intramolecular Cyclization/Electrophilic Substitution of Urea Derivatives and the Evaluation of Their Anticancer Activity

A series of novel 4-(het)arylimidazoldin-2-ones were obtained by the acid-catalyzed reaction of (2,2-diethoxyethyl)ureas with aromatic and heterocyclic C-nucleophiles. The proposed approach to substituted imidazolidinones benefits from excellent regioselectivity, readily available starting materials and a simple procedure. The regioselectivity of the reaction was rationalized by quantum chemistry calculations and control experiments. The anti-cancer activity of the obtained compounds was tested in vitro.

Zirconium complexes supported by a ferrocene-based ligand as redox switches for hydroamination reactions

The synthesis of (thiolfan*)Zr(NEt2)2 (thiolfan* = 1,1'-bis(2,4-di-tert-butyl-6-thiophenoxy)ferrocene) and its catalytic activity for intramolecular hydroamination are reported. In situ oxidation and reduction of the metal complex results in reactivity towards different substrates. The reduced form of (thiolfan*)Zr(NEt2)2 catalyzes hydroamination reactions of primary aminoalkenes, whereas the oxidized form catalyzes hydroamination reactions of secondary aminoalkenes.

Intramolecular hydroamination reactions catalyzed by zirconium complexes bearing bridged bis(phenolato) ligands

Cationic species derived from zirconium complexes stabilized by bridged bis(phenolato) ligands showed good activities in catalyzing intramolecular hydroamination/cyclization of primary and secondary amines.

Cationic Group-IV pincer-type complexes for polymerization and hydroamination catalysis

Neutral Zr(IV) and Hf(IV) dimethyl complexes stabilized by unsymmetrical dianionic {N,C,N'} pincer ligands have been prepared from their corresponding bis-amido complexes upon treatment with AlMe3. Their structure consists of a central σ-bonded aryl donor group (C) capable of forming robust M-C bonds with the metal center, enforced by the synergic effect of both the coordination of peripheral donor groups (N) and the chelating rigid structure of the {N,C,N} ligand framework. Such a combination translates into systems having a unique balance between stability and reactivity. These Zr(IV) and Hf(IV) dimethyl complexes were converted in situ into cationic species [M(IV){N(-),C(-),N}Me][B(C6F5)4] which are active catalysts for the room temperature (r.t.) intramolecular hydroamination/cyclization of primary and secondary aminoalkenes as well as for the high temperature ethylene-1-octene copolymerizations.

Group IV organometallic compounds based on dianionic "pincer" ligands: synthesis, characterization, and catalytic activity in intramolecular hydroamination reactions

Neutral Zr(IV) and Hf(IV) diamido complexes stabilized by unsymmetrical dianionic N,C,N' pincer ligands have been prepared through the simplest and convenient direct metal-induced Caryl-H bond activation. Simple ligand modification has contributed to highlight the non-innocent role played by the donor atom set in the control of the cyclometallation kinetics. The as-prepared bis-amido catalysts were found to be good candidates for the intramolecular hydroamination/cyclization of primary aminoalkenes. The ability of these compounds to promote such a catalytic transformation efficiently (by providing, in some cases, fast and complete substrate conversion at room temperature) constitutes a remarkable step forward toward catalytic systems that can operate at relatively low catalyst loading and under milder reaction conditions. Kinetic studies and substrate-scope investigations, in conjunction with preliminary DFT calculations on the real systems, were used to elucidate the effects of the substrate substitution on the catalyst performance and to support the most reliable mechanistic path operative in the hydroamination reaction.

Asymmetric hydroamination catalyzed by in situ generated chiral amidate and ureate complexes of zirconium — Probing the role of the tether in ligand design

Simple chiral proligands have been synthesized from inexpensive chiral starting materials. These amidate and ureate ligands support zirconium complexes that successfully catalyze intramolecular hydroamination with up to 26% ee. Several elements necessary for successful ligand design are highlighted and discussed. In particular, the strict control of metal geometry through multidentate tethered ligands is determined to be an essential aspect of future ligand development.