A new class of urea-substituted cinchona alkaloids promote highly enantioselective nitroaldol reactions of trifluoromethylketones

The first class of bifunctional cinchona-alkaloid catalysts incorporating a urea moiety at C-5' has been developed. These materials catalyze the efficient and highly enantioselective 1,2-addition of nitromethane to trifluoromethylketones to form synthetically pliable products incorporating a quaternary stereocenter. Excellent product yields and levels of enantiomeric excess are possible, and the optimum catalyst structure is capable of promoting the Henry reaction involving alkyl trifluoromethylketones with unprecedented enantioselectivity.     

Chiral 2-(2-Diphenylphosphinophenyl)-oxazolines: Synthesis and Use in Pd-Catalyzed Asymmetric Allylic Alkylation

The synthesis of 2-(2-diphenylphosphinophenyl)-oxazolines from o-fluoroben-zonitrile and (-)-norephedrine or (+)-endo-2-hydroxy-endo-3-aminobornane is described. The Pa-catalyzed alkylation of (E)-1,3-diphenylallyl acetate with the sodium salt of dimethylmalonate using these chiral ligands occurs with an 82–87% yield and 88–93% ee.     

Unprecedented lanthanide-containing coordination polymers constructed from hexanuclear molecular building blocks: {[Ln6O(OH)8](NO3)2(bdc)(Hbdc)2·2NO3·H)bdc}∞

Reactions in acetonitrile between 1,4-benzene-dicarboxylic acid (C(8)H(6)O(4)) and a hexanuclear complex of lanthanide [Ln(6)O(OH)(8)(NO(3))(6)·2NO(3)] with Ln = Y or Tb lead to 1D-coordination polymers with the general chemical formula {[Ln(6)O(OH)(8)](NO(3))(2)(bdc)(Hbdc)(2)·2NO(3)·H(2)bdc}(∞) where H(2)bdc stands for 1,4-benzene-dicarboxylic acid (or terephthalic acid). These two compounds are isostructural. The crystal structure has been solved on the basis of the X-ray powder diffraction diagram of the Y-containing compound. This compound crystallizes in the triclinic system, space group P1 (no. 2) with a = 10.4956(6) ?, b = 11.529(2) ?, c = 12.357(2) ?, α = 86.869(9)°, β = 114.272(6)°, γ = 71.624(7)°, V = 1264.02 ?(3), and Z = 2. The crystal structure can be described as the juxtaposition of linear chains of hexanuclear entities linked to each other by terephthalate ligands. Two additional partially protonated terephthalate ligands spreading laterally to the chain are bound to each hexanuclear entity. Another diprotonated terephthalic ligand and two nitrate ions ensuring the electroneutrality of the crystal structure lie in the interchain space. These two compounds are thermally stable until 200 °C. Thanks to a so-called antenna effect, the Tb-containing compound, despite short intermetallic distances, exhibits a strong luminescence under UV irradiation.     

An Artificial Intelligence Approach for Tackling Conformational Energy Uncertainties in Chiroptical Spectroscopies

Determination of the absolute configuration of chiral molecules is a prerequisite for obtaining a fundamental understanding in any chirality-related field. The interaction with polarised light has proven to be a powerful means to determine this absolute configuration, but its application rests on the comparison between experimental and computed spectra for which the inherent uncertainty in conformational Boltzmann factors has proven to be extremely hard to tackle. Here we present a novel approach that overcomes this issue by combining a genetic algorithm that identifies the relevant conformers by accounting for the uncertainties in DFT relative energies, and a hierarchical clustering algorithm that analyses the trends in the spectra of the considered conformers and identifies on-the-fly when a given chiroptical technique is not able to make reliable predictions. The effectiveness of this approach is demonstrated by considering the challenging cases of papuamine and haliclonadiamine, two bis-indane natural products with eight chiral centres and considerable conformational heterogeneity that could not be assigned unambiguously with current approaches.