Infrared Fourier Transform Spectroscopy (DRIFTS). In the case of pure NiO, we found that the surface of the support was mainly covered by elemental Ni under reaction condition, where the Ni/NiO x system is responsible for the high activity of Pt-free catalyst. In the case of Pt/NiO, Pt improves the reduction of NiO x towards metallic Ni. In the case of the 1 % Pt/NiO catalysts, the presence of limited amount of Pt resulted in an optimal quantity of oxidized Pt fraction at 673 K showing the presence of a Pt/PtO x /Ni/NiO x mixed phase where the different interfaces may be responsible for the high activity and selectivity towards methane. In the case of pure NiO under reaction condition, small amounts of formaldehyde as well as hydrogen perturbed CO [H n CO (n=1,2)] were detected. However, in the case of 1 % Pt/NiO catalysts, besides the absence of formaldehyde a significant amount of H n CO (n=2-3) was present on the surface responsible for the high activity and methane selectivity.

Unprecedentedly high enantioselectivities are obtained in the transfer hydrogenation of prochiral ketones catalyzed by a Ru complex formed in situ with chitosan chiral ligand. This biocompatible, biodegradable chiral polymer obtained from the natural chitin afforded good, up to 86 % enantioselectivities, in the aqueous‐phase transfer hydrogenation of acetophenone derivatives using HCOONa as hydrogen donor. Cyclic ketones were transformed in even higher, over 90 %, enantioselectivities, whereas further increase, up to 97 %, was obtained in the transfer hydrogenations of heterocyclic ketones. The chiral catalyst precursor prepared ex situ was examined by scanning electron microscopy, FT‐mid‐ and ‐far‐IR spectroscopy. The structure of the in situ formed catalyst was investigated by 1H NMR spectroscopy and using various chitosan derivatives. It was shown that a Ru pre‐catalyst is formed by coordination of the biopolymer to the metal by amino groups. This precursor is transformed in water insoluble Ru‐hydride complex following hydrogen donor addition. The practical value of the developed method was verified by preparing over twenty chiral alcohols in good yields and optical purities. The catalyst was applied for obtaining optically pure chiral alcohols at gram scale following a single crystallization.

The present study aimed at extending the applicability of a recently developed stereoselective catalytic system to the preparation of optically enriched N‐heterocyclic alcohols. Chiral ruthenium catalyst formed in situ using the chitosan biopolymer as ligand, which provided good results in the transfer hydrogenation of heterobicyclic compounds, such as 4‐chromanone and 4‐thiochromanone, was used in reactions of various N‐containing prochiral ketones. High enantioselectivities were reached in transfer hydrogenations of bicyclic compounds bearing nitrogen either in aromatic or cycloaliphatic moieties, provided that the amino group was protected or shielded by a nearby substituent. Results were rationalized by interactions of the nitrogen with the metal and/or ligand. N‐containing bicyclic compounds having heteroatoms in both rings were also prepared and tested. The detrimental effect of the pyridyl moiety was compensated by the beneficial influence of the heteroatom in the cycloaliphatic ring, as indicated by high rates and good enantioselectivities obtained in reactions of these compounds. Preparation of several N‐heterocyclic alcohols, in good yields and high optical purities was achieved using Ru(II)‐chitosan complex.

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Dedicated to the memory of Prof. Ferenc FülöpAsymmetric catalytic reactions are among the most convenient and environmentally benign methods to obtain optically pure compounds. The aim of this study was to develop a green system for the asymmetric transfer hydrogenation of ketones, applying chiral Ru catalyst in aqueous media and mechanochemical energy transmission. Using a ball mill we have optimized the milling parameters in the transfer hydrogenation of acetophenone followed by reduction of various substituted derivatives. The scope of the method was extended to carbo-and heterocyclic ketones. The scale-up of the developed system was successful, the optically enriched alcohols could be obtained in high yields. The developed mechanochemical system provides TOFs up to 168 h À 1 . Our present study is the first in which mechanochemically activated enantioselective transfer hydrogenations were carried out, thus, may be a useful guide for the practical synthesis of optically pure chiral secondary alcohols.