The performance of computationally accessible levels of calculation for the transition states of organocatalytic reaction has been assessed. Reference post-Hartree-Fock single point energy calculations were used as standards for the gas-phase Born-Oppenheimer relative energies of pairs of alternative transition states that lead to the two product enantiomers. We show that semiempirical methods cannot even be relied on to yield qualitatively correct results. The geometries (optimized, for instance, with DFT) have a large impact on the results of high-level post-HF calculations, so that it is essential to use an adequate DFT technique and basis set. DFT can yield quantitatively correct results that are consistent with post-HF calculations if functionals that consider dispersion are used. Geometries for large systems show larger errors than those for smaller ones but are treated better by functionals such as M06-2X and w97Bxd that include dispersion implicitly or explicitly. Local correlation techniques introduce errors of comparable magnitude to those given by different levels of geometry optimization. We recommend RICC2/TZVP//M06-2X/TZVP, RI-MP2/TZVP// M06-2X/TZVP, and M06-2X/TZVP// M06-2X/TZVP calculations in that order, depending on the size of the system.

BINOL-derived phosphoric acids have emerged during the last five years as powerful chiral Brønsted acid catalysts in many enantioselective processes. The most successful transformations carried out with chiral BINOL phosphates include C-C bond formation reactions. The recent advances have been reviewed in this article with a focus being placed on hydrocyanations, aldol-type, Mannich, Friedel-Crafts, aza-ene-type, Diels-Alder, as well as cascade and multi-component reactions.

Cinchonidine (CD) adsorbed onto a platinum metal catalyst leads to rate acceleration and induces strong stereocontrol in the asymmetric hydrogenation of trifluoroacetophenone. Addition of catalytic amounts of trifluoroacetic acid (TFA) significantly enhances the enantiomeric excess from 50 to 92%. The origin of the enantioselectivity bestowed by co-adsorbed CD and TFA is investigated by using in situ attenuated total reflection infrared spectroscopy and modulation excitation spectroscopy. Molecular interactions between the chiral modifier (CD), acid additive (TFA) and the trifluoro-activated substrate at the solid-liquid interface are elucidated under conditions relevant to catalytic hydrogenations, that is, on a technical Pt/Al2O3 catalyst in the presence of H2 and solvent. Monitoring of the unmodified and modified surface during the hydrogenation provides an insight into the phenomenon of rate enhancement and the crucial interactions of CD with the ketone, corresponding product alcohol, and TFA. Comparison of the diastereomeric interactions occurring on the modified surface and in the liquid solution shows a striking difference for the chiral preferences of CD. The spectroscopic data, in combination with calculations of molecular structures and energies, sheds light on the reaction mechanism of the heterogeneous asymmetric hydrogenation of trifluoromethyl ketones and the involvement of TFA in the diastereomeric intermediate surface complex: the quinuclidine N atom of the adsorbed CD forms an N-H-O-type hydrogen-bonding interaction not only with the trifluoro-activated ketone but also with the corresponding alcohol and the acid additive. Strong evidence is provided that it is a monodentate acid/base adduct in which the carboxylate of TFA resides at the quinuclidine N-atom of CD, which imparts a better stereochemical control.

Keywords: Organocatalysis / Brønsted acids / Lewis acids / Hydrogen bonds / Binaphthyl derivativesIn recent years, binaphthyl compounds have found frequent applications in the design of various asymmetric organocatalysts, because binaphthyl structures are an attractive platform for organocatalyst development, particularly in light of their axial chirality characteristic. In this review, we discuss

A first and fairly mild metal-free catalytic route was developed for the [3+2] cycloadditions of different N-acylhydrazones to cyclopentadiene, providing the synthetically and biologically important five-membered cyclic compounds pyrazolidines. The reaction was successfully conducted in high yields (up to 99 %) with high diastereoselectivities (up to 98:2 dr) by using catalytic amounts of TMSOTf (trimethylsilyl

For developing sustainable products design engineers need to foresee diverse interrelations between a product's characteristics and its economic, social and environmental impacts. In order to support this complex task a wide range of design methods has been developed. Retrospective analytical methods like Life Cycle Sustainability Assessment (LCSA) require a large amount of information and are thus utilized when important design decisions are already made. Prospective methods are rather generic (e.g. checklists) and too broad to be helpful in concrete design decisions. In this paper, the integration of discrete decision trees with LCSA is proposed for shifting multi-criterial quantitative analysis to earlier development. On the basis of sustainability indicators Pareto-optimal decision-paths for given material-and process alternatives along the product lifecycle can be compared up-front. Resulting benefits and obstacles are illustrated by evaluating value creation options of a bicycle frame.

Simple unmodified N-proline-based di- and tripeptides in combination with sodium hydroxide additive catalyze the asymmetric Michael reaction of ketones with nitroolefins to furnish the corresponding gamma-nitroketones with up to 99% yield, 99:1 dr and 70% ee at room temperature and on water without any organic cosolvent.

SummaryA new guanidine-thiourea organocatalyst has been developed and applied as bifunctional organocatalyst in the Michael addition reaction of diethyl malonate to trans-β-nitrostyrene. Extensive DFT calculations, including solvent effects and dispersion corrections, as well as ab initio calculations provide a plausible description of the reaction mechanism.