Nuovi Complessi Carbossilati di Rutenio Contenenti Difosfine Elettron-ricche per la sintesi di Molecole di Interesse Alimentare e Biologico

The aim of this thesis was the synthesis of novel catalytic systems based on acetate ruthenium complexes, bearing basic and relatively bulky diphosphines and their application in the reduction of carbonyl substrates to their corresponding alcohols, with molecular hydrogen and via transfer hydrogenation reaction using 2-propanol as hydrogen source. Moreover, the employment of these systems as catalysts in the alkylation of aliphatic and aromatic amines with primary alcohols and diols via borrowing hydrogen was studied. In addition. The work performed on this subject can be split out into four parts as follows: 1. The first part has concerned the synthesis and the characterization of the complexes Ru(OAc)2(PP) [PP=1,1\u2019-bis(diisopropylphosphino)ferrocene; 1,1\u2019-bis(dicyclohexylphosphino)ferrocene), Ru(OAc)2(PP)(NN) (NN= 2-(aminomethyl)pyridine; ethylenediamine)and the monocarbonyl derivatives Ru(OAc)2(CO)(PP). 2. The second part has been focused on the study on the catalytic performances of Ru(OAc)2(PP) and in situ generated Ru(OAc)2(PP)(NN) in the transfer hydrogenation of carbonyl compounds in basic 2-propanol 3. During the third part the unprecedented hydrogenation of benzaldehyde in neat conditions (solvent-less) catalyzed by Ru(OAc)2(CO)(PP) with hydrogen at low and high pressure, has been studied, affording benzyl alcohol with high purity. The scope of this reaction has been extended to different aromatic and \u3b1,\u3b2-unsaturated aldehydes, with high chemoselectivity for the C=O vs. C=C bond, and to ketone and imine substrates, under basic and also acidic conditions at very high S/C (105). In particular, trans-cinnamaldehyde, citral have been reduced to the corresponding food relevant alcohols. 4. The final part has regarded the application of the new developed Ru(OAc)2(CO)(PP) systems in the ethylation of N-ethylcyclohexylamine with ethanol via borrowing hydrogen at relatively mild conditions (30 - 100 \ub0C). To broaden the scope of this transformation, primary aliphatic and aromatic amines and different alkylating agents, including diols allowing formation of substituted pyrrolidines and piperazines, have been employed. Intramolecular reaction of 2-hydroxyethylaniline has also been investigated to obtain indoles, which as the pyrrolidine and piperazine derivatives are biologically relevant pharma frameworks. The wide reactivity and productivity exhibited by these new class of ruthenium catalysts make them very attractive for industrial applications

Highly Efficient Hydrogenation Ruthenium and Osmium Catalysts based on Ampy type Ligands

Ruthenium phosphine complexes have been widely examined in homogeneous hydrogenation (HY) and transfer hydrogenation reactions (TH), which are cost-effective and environmentally benign ways accepted in the industry for the reduction of carbonyl compounds. On account of the reversibility of the C-H bond activation, ruthenium catalysts have attracted a great deal of interest for a number of organic transformations, including borrowing hydrogen reactions. In this context, the design of efficient chelating and non-innocent ligands is crucial to achieve high activity and retard catalyst deactivation. Highly efficient Ru and Os catalysts for both TH and HY reactions were obtained by our group with ligands based on the 2-(aminomethyl)pyridine motif (A). More productive catalysts were subsequently developed by employment of pincer terdentate CNN ligands showing a metal-carbon \u3c3-bond (B).1 These complexes allow fast reduction of ketones and aldehydes, including some biomass derivatives (5-HMF, ethyl levulinate), with H2, 2-propanol or ammonium formate at S/C up to 105. Employment of chiral catalysts in the ketone reduction afforded alcohols with up to 99% ee. The Ru and Os derivatives A and B can also catalyze the acceptorless DHY of alcohols to ketones and other transformations involving alcohol C-H activation, namely alcohol racemization, deuteration and ketone \u3b1-alkylation. Evidence has been provided that the catalytically active Ru hydride species are in rapid equilibrium with metal-amino alkoxides

Pincer and Carbonyl Ruthenium Complexes for Transfer Hydrogenation Reactions

The transfer hydrogenation (TH) catalyzed by ruthenium complexes is a cost-effective and environmentally benign way for the reduction of carbonyl compounds. On account of the reversibility of the TH process, ruthenium catalysts have attracted a great deal of interest for a number of C-H activation organic transformations. To improve the catalytic activity and to retard decomposition, the design of suitable chelating and non-innocent ligands appears crucial. We report here the preparation of pincer, carbonyl and acetate ruthenium complexes, displaying high productivity for the TH of carbonyl compounds, including flavanones and biomass-derived molecules (5-HMF, ethyl levulinate). The alkylation of amines with alcohols and the preliminary results on the photochemical TH of carbonyl compounds are also presented

Mild N-Alkylation of Amines with Alcohols Catalyzed by Acetate Ruthenium Complexes

The formation of C-N bonds for the preparation of amines compounds is a reaction of high relevance for the synthesis of bulk and fine chemicals (1). The preparation of several drug molecules involves N-substitution transformations that are usually performed by reaction of amines with alkylating agents or via reductive amination. In this context, the catalytic Nalkylation of amines using environmentally friendly alcohols as alkylating reagents and affording water as only byproduct, is an attractive atom-economic way for the C-N bond formation (2,3). We report here the straightforward synthesis of the carboxylate ruthenium complexes of formula Ru(OAc)2(diphosphane)(CO)n (n = 0, 1). These compounds are efficient catalysts for the N-alkylation of amines using primary alcohols under mild reaction conditions, with an alcohol / amine molar ratio of 10-100. Evidence has been provided that in catalysis a monohydride species is formed through an equilibrium reaction

Cyclometallated Ruthenium Complexes for Transfer Hydrogenation and Hydrogenation Reactions

The catalytic hydrogenation and transfer hydrogenation of carbonyl compounds to alcohols is a reaction of broad application in the industry, resulting in a lower environmental impact and an easier work-up with respect to the classical approach with NaBH4, LiAlH4 and Al alkoxides.1 The search of well-designed and productive catalysts of ruthenium, which is cheaper with respect to rhodium and iridium, has led to a number of efficient hydrogenation systems. We report here the isolation of highly active ruthenium cyclometallated CNN and PC catalysts containing the ampy motif2 with phosphine and CO ligands, starting from phosphine and carbonyl Ru precursors. The presence of a metal-carbon \u3c3-bond leads to robust and productive catalysts for the reduction of commercial-grade aldehydes and (bulky) ketones using H2 (5-30 atm), 2-propanol or ammonium formate,3 with S/C up to 100000 and TOF up to 100000 h-1. Acknowledgements We gratefully acknowledge the financial support from MIUR (PRIN 2015, n\ub0 20154X9ATP_005) References 1. (a) Xie, X.; Lu, B.; Li, W.; Zhang, Z. Coord. Chem. Rev. 2018, 355, 39. (b) Wang, D.; Astruc, D. Chem. Rev. 2015, 115, 6621. 2 Chelucci, G.; Baldino, S.; Baratta, W. Coord. Chem. Rev. 2015, 300, 29. 3 Baldino, S.; Facchetti, S.; Nedden, H. G.; Zanotti-Gerosa, A.; Baratta, W. ChemCatChem, 2016, 8, 3195

Bulky Diphosphine Acetate Ruthenium Complexes: Synthesis and Catalytic Activity in Ketone Transfer Hydrogenation and Alkyne Dimerization

Several mononuclear ruthenium complexes containing bulky diphosphines have been easily prepared from acetate ruthenium precursors. The cyclohexyl complex [Ru(η2-OAc)2(DCyPF)] (1-cy; DCyPF = 1,1′-bi..