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The homogeneously catalyzed Guerbet upgrading of ethanol to butanol can be modulated by the application of partial H2 pressure before the reaction. Ruthenium(II) PNP pincer complexes with methylene‐extended acridine‐based ligands and singly‐chelated ruthenium(II) complexes with PN ligands perform best at very low catalyst loadings and upon the application of catalyst‐specific pre‐reaction partial H2 pressure. The combination of ruthenium(II) PNP pincer complexes and manganese(I) pincer complexes with MACHO‐type PNP ligands allows for even lower ruthenium loadings while retaining low base load and consumption, thus enabling high space‐time yields, catalyst productivity and recyclability. Mechanistically, Mn is proposed to stabilize coordinatively unsaturated Ru species and allow coordination of ethoxide to Ru instead of attacking the electrophilic ligand backbone based on NMR spectroscopy and X‐ray crystallography. [ABSTRACT FROM AUTHOR]

The influence of the ligand backbone on the enantioselectivity in the ruthenium‐catalyzed direct asymmetric reductive amination of acetophenone with NH3 and H2, using bidentate binaphthyl‐substituted phosphine ligands, was investigated in a combined computational and experimental study. A model for the bite angle dependence of the enantiomeric excess (ee) when using diphosphines bearing binaphthyl‐groups on the P‐atoms was developed. This revealed a significant potential for increasing the enantioselectivity, if ligands with a larger bite angle than the previously reported (S,S)‐f‐binaphane are used. Suitable backbone candidates were selected from more than one million structures provided by the Cambridge Structural Database (CCDC‐CSD) and the most promising candidates were synthesized accordingly. Despite all efforts, an increase of the ee was not possible with this approach. The larger backbones resulted in the preference of different ligand coordination modes avoiding the formation of the more strongly enantiodiscriminant substrate pocket between the naphthyl wings. [ABSTRACT FROM AUTHOR]

Sugar alcohols are of great importance for the food industry and are promising building blocks for bio‐based polymers. Industrially, they are produced by heterogeneous hydrogenation of sugars with H2, usually with none to low stereoselectivities. Now, we present a homogeneous system based on commercially available components, which not only increases the overall yield, but also allows a wide range of unprotected ketoses to be diastereoselectively hydrogenated. Furthermore, the system is reliable on a multi‐gram scale allowing sugar alcohols to be isolated in large quantities at high atom economy. [ABSTRACT FROM AUTHOR]

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The direct conversion of ketones into chiral primary amines is a key transformation in chemistry. Here, we present a ruthenium catalyzed asymmetric reductive amination (ARA) of purely aliphatic ketones with good yields and moderate enantioselectivity: up to 99 % yield and 74 % ee. The strategy involves [Ru(PPh3)3H(CO)Cl] in combination with the ligand (S,S)‐f‐binaphane as the catalyst, NH4I as the amine source and H2 as the reductant. This is a straightforward and user‐friendly process to access industrially relevant chiral aliphatic primary amines. Although the enantioselectivity with this approach is only moderate, to the extent of our knowledge, the maximum ee of 74 % achieved with this system is the highest reported till now apart from enzyme catalysis for the direct transformation of ketones into chiral aliphatic primary amines. [ABSTRACT FROM AUTHOR]

A new approach for the efficient and highly selective synthesis of 1,2‐amino alcohols by direct reductive hydrolysis of N‐formyl‐protected α‐amino nitriles is reported. The commercially available RuHCl(CO)(PPh3)3 complex was found to be a suitable catalyst for this operationally simple protocol, in which no stoichiometric amounts of undesired metal waste are generated. The deaminative hydrogenation is performed at 55 bar of H2, using a 6:1 mixture of 1,4‐dioxane/water as solvent. In addition, hydroxymethyl alcohols were prepared from cyanoketones under very similar conditions. [ABSTRACT FROM AUTHOR]

The deaminative hydrogenation of nitriles towards alcohols is a useful reaction to transform nitriles into alcohols with NH3 as the sole byproduct. Using the simple and robust RuHCl(CO)(PPh3)3 complex as a catalyst, at low H2 pressures a series of aliphatic and aromatic nitriles could be transformed into the corresponding alcohols. Suitable solvent systems for these reactions were 1,4-dioxane/water and EtOH/water mixtures. In most cases, the selectivity for the alcohols was excellent, and the corresponding amines were formed only in trace amounts. [ABSTRACT FROM AUTHOR]

A highly selective reductive amination of ketones to primary amines with ammonia and hydrogen using a simple ruthenium catalyst has been developed. The protocol described constitutes an efficient and direct atom-economical approach en route to α-methylbenzylamine derivatives in good to high yields. The presence of catalytic amounts of aluminum triflate turned out to be crucial for achieving high conversion towards primary amines. [ABSTRACT FROM AUTHOR]