Die asymmetrische Addition terminaler Inamide an Trifluormethylketone mit einem leicht zugänglichem chiralen Zink-Katalysator ergibt CF₃-substituierte tertiäre Propargylalkohole mit bis zu 99 % Ausbeute und 96 % ee. Der Ausschluss von organischen Zinkadditiven und Basen sowie der Nutzen der Produkte für Synthesen sind besondere Merkmale dieser Reaktion. Der Wert der β-Hydroxy-β-trifluormethylinamide ist exemplarisch mit ausgewählten Umwandlungen zu chiralen Z- und E-Enamiden, einem Amid und N,O-Ketenacetalen belegt. Die äußerst regioselektive Hydratisierung, stereoselektive Reduktionen und Hydroacyloxylierungen erfolgen mit hohen Ausbeuten und ohne Erosion des ee der verwendeten β-Hydroxyinamide.

The asymmetric addition of terminal ynamides to trifluoromethyl ketones with a readily available chiral zinc catalyst gives CF₃-substituted tertiary propargylic alcohols in up to 99 % yield and 96 % ee. The exclusion of organozinc additives and base as well as the general synthetic utility of the products are key features of this reaction. The value of the β-hydroxy-β-trifluoromethyl ynamides is exemplified by selective transformations to chiral Z- and E-enamides, an amide, and N,O-ketene acetals. The highly regioselective hydration, stereoselective reduction, and hydroacyloxylation reactions proceed with high yields and without erosion of the ee value of the parent β-hydroxy ynamides.

Two bidentate ligands consisting of a fluxional polyarylacetylene framework with terminal phenol groups were synthesized. Reaction with diethylzinc gives stereodynamic complexes that undergo distinct asymmetric transformation of the first kind upon binding of chiral amines and amino alcohols. The substrate-to-ligand chirality imprinting at the zinc coordination sphere results in characteristic circular dichroism signals that can be used for direct enantiomeric excess (ee) analysis. This chemosensing approach bears potential for high-throughput ee screening with small sample amounts and reduced solvent waste compared to traditional high-performance liquid chromatography methods. Chirality 27:700–707, 2015. © 2015 Wiley Periodicals, Inc.

Coordination of a chiral substrate to (meso-salen)cobalt(II) nitrate and subsequent oxidation generates a Co(III) complex exhibiting a strong chiroptical readout that is attributed to spontaneous substrate-to-ligand chirality imprinting. The characteristic circular dichroism (CD) response of the (salen)cobalt complex can be used for enantiomeric analysis of a variety of chiral substrates based on a simple CD measurement at low concentration and without additional purification steps. This chirality sensing approach has potential for high-throughput enantiomeric excess (ee) screening applications and minimizes solvent waste production. Chirality 26:379–384, 2014. © 2014 Wiley Periodicals, Inc.

Enantioselective induced circular dichroism analysis of amino alcohols has been accomplished using a conformationally flexible arylacetylene-based probe exhibiting two terminal aldehyde groups. The chirality of the amino alcohol substrates is imprinted on the stereodynamic receptor upon [1 + 2] condensation, which ultimately generates a strong chiroptical response. The distinct induced circular dichroism effects of the diimines obtained can be used for enantioselective sensing and enantiomeric excess determination of a wide range of substrates. Chirality 24:584–589, 2012. © 2012 Wiley Periodicals, Inc.

Bisoxazolidine 1 is an effective ligand in the copper(I)-catalyzed Friedel–Crafts reaction of alkyl trifluoropyruvates and indoles. A range of ethyl 2-(3′-indolyl)-3,3,3-trifluoro-2-hydroxypropanoates was produced in up to 99% yield and 94% ee within 30 min to 4 h. The effect of temperature on conversion and enantioselectivity proved to be substrate specific and was optimized individually. Of particular interest is that this method tolerates the presence of substituents in various positions in the indole ring. Yields ranging from 90–97% and ee values between 90 and 94% were obtained at optimized temperatures with substrates carrying substituents in position 1 or 7.

During recent years, the direct transformation of aldehydes into esters or amides has developed into a vigorous research area and powerful one-pot oxidative esterification and amidation procedures have been reported. Several concepts that are often complementary in substrate scope, functional group tolerance, and reaction outcome have emerged, thus providing a wide range of alternatives to classical ester and amide synthesis via carboxylic acid intermediates.