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.
The origin of the single chirality of most biomolecules is still a great puzzle. Carbohydrates could form in the formose reaction, which is proposed to be autocatalytic and contains aldol reaction steps. Based on our earlier observation of organoautocatalysis and spontaneous enantioenrichment in absence of deliberate chiral influences in the aldol reaction of acetone and p-nitrobenzaldehyde we suggest that a similar effect might be present also in the aldol reactions involved in gluconeogenesis. Herein we show that reactant precipitation observed in our earlier reported experiments does not affect the asymmetric autocatalysis in the aldol reaction we studied. We explain the phenomenon of spontaneous mirror symmetry breaking in such organocatalytic homogenous systems qualitatively by non-linear reaction network kinetics and classical transition state theory.
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
Rückwärts zum Ziel: Ausgehend von einem Konglomerat von 1 mit niedrigem Enantiomerenüberschuss werden in Gegenwart racemischer oder achiraler Katalysatoren asymmetrische Verstärkungen von bis zu 100 % ee erzielt, wenn man Vorwärts‐ und Rückwärtsreaktionsschritte eines reversiblen chemischen Prozesses (siehe Schema) mit den physikalischen Prozessen der Kristallisation, Kristallzermahlung und Auflösung verbindet.
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.
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