Selective and Scalable Synthesis of Sugar Alcohols by Homogeneous Asymmetric Hydrogenation of Unprotected Ketoses.

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 H , 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.

Ru or Ru: A Study on Stabilizing the "Activated" Form of Ru-PNP Complexes with Additional Phosphine Ligands in Alcohol Dehydrogenation and Ester Hydrogenation.

The complex Ru-MACHO has been previously shown to undergo uncontrolled degradation subsequent to base-induced dehydrochlorination in the absence of a substrate. In this study, we report that stabilization of the dehydrochlorinated Ru-MACHO with phosphines furnishes complexes whose structures depend on the phosphines employed: while PMe led to the expected octahedral Ru complex, PPh provided access to a trigonal-bipyramidal Ru complex. Because both complexes proved to be active in base-free (de)hydrogenation reactions, thorough quantum-chemical calculations were employed to understand the reaction mechanism.

Exploring unsymmetrical diboranes(4) as boryl ligand precursors: platinum(ii) bis-boryl complexes.

A series of five unsymmetrical platinum(ii) bis-boryl complexes, bearing two distinct boryl ligands, are obtained by the oxidative addition reaction of unsymmetrical diborane(4) derivatives, bearing either two different dialkoxy or one dialkoxy and one diamino boryl moiety, with [(PhP)Pt(CH)]. All five complexes were structurally and spectroscopically characterised. The bis-boryl platinum(ii) complexes exhibit slightly distorted square-planar -boryl structures with acute B-Pt-B angles, short B⋯B distances of 2.

Structure and Reactivity of Half-Sandwich Rh(+3) and Ir(+3) Carbene Complexes. Catalytic Metathesis of Azobenzene Derivatives.

Traditional rhodium carbene chemistry relies on the controlled decomposition of diazo derivatives with [Rh(OAc)] or related dinuclear Rh(+2) complexes, whereas the use of other rhodium sources is much less developed. It is now shown that half-sandwich carbene species derived from [Cp*MX] (M = Rh, Ir; X = Cl, Br, I, Cp* = pentamethylcyclopentadienyl) also exhibit favorable application profiles. Interestingly, the anionic ligand X proved to be a critical determinant of reactivity in the case of cyclopropanation, epoxide formation and the previously unknown catalytic metathesis of azobenzene derivatives, whereas the nature of X does not play any significant role in -OH insertion reactions.

Analyzing site selectivity in Rh2(esp)2-catalyzed intermolecular C-H amination reactions.

Predicting site selectivity in C-H bond oxidation reactions involving heteroatom transfer is challenged by the small energetic differences between disparate bond types and the subtle interplay of steric and electronic effects that influence reactivity. Herein, the factors governing selective Rh2(esp)2-catalyzed C-H amination of isoamylbenzene derivatives are investigated, where modification to both the nitrogen source, a sulfamate ester, and substrate are shown to impact isomeric product ratios. Linear regression mathematical modeling is used to define a relationship that equates both IR stretching parameters and Hammett σ(+) values to the differential free energy of benzylic versus tertiary C-H amination.

Imidazolidin-2-one: pseudosymmetry and twinning.

The title compound, C3H6N2O, crystallizes with imposed twofold symmetry in the space group I4(1)/a. The five-membered ring displays a half-chair conformation. N-H···O hydrogen bonds connect the molecules to form R2(2)(8) rings and thence ribbons parallel to the a and b axes.