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’-bis(diisopropylphosphino)ferrocene; 1,1’-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 α,β-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 °C). 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.
