نتایج جستجو برای: achiral
تعداد نتایج: 1375 فیلتر نتایج به سال:
The degree of order of poly(3-alkylthiophene)s on atomically flat surfaces is strongly influenced by interchain interactions. Regularly ordered, disordered and amorphous microstructures are observed for achiral, homochiral and meso poly(3-alkylthiophene)s, respectively, as revealed by scanning tunneling microscopy.
An enantioselective vinylogous umpolung addition of deconjugated butenolides to allenoates has been developed for the first time with the help of synergistic combination of an achiral phosphine and a chiral squaramide, and represents the first example of a catalytic enantioselective Cγ-Cγ bond formation between two different carbonyl partners.
A homochiral helical coordination polymer of copper(II) has been synthesized using achiral precursors via spontaneous symmetry breaking and has been confirmed by single crystal X-ray diffraction and solid-state CD spectroscopy. The variable temperature magnetic measurements indicate the presence of weak ferromagnetic exchange interactions mediated by end-to-end cyanate bridges (J = +0.12 cm(-1)).
The achiral liquid crystalline materials showing two B4 (HN) phases have been found to exhibit strong gelation ability for various organic solvents with reversible sol-gel phase transition. The gel is formed by helical tubules, which build entangled 3D network, encapsulating the solvent. The equilibrium of left- and right-handed tubules is preserved in the gel, even if the chiral solvent is used.
The kinetics of enantiomerization and dynamic thermodynamic resolution (DTR) of N-Boc-2-lithiopiperidine have been measured, revealing significant differences in enthalpy and entropy for these processes and a role for the achiral ligand TMEDA; the racemization and the DTR are catalytic and first order in [TMEDA], and this has implications for asymmetric synthesis with chiral organolithiums.
A highly fluorescent organogel with transparency was formed through a hydrogen (H)-bonding interaction between a non-fluorescent and achiral 2-(3',5'-bis-trifluoromethyl-biphenyl-4-yl)-3-(4-pyridin-4-yl-phenyl)-acrylonitrile (CN-TFMBPPE) monomer and chiral sergeant l-tartaric acid (TA) (or d-TA), with gel formation being accompanied by a drastic fluorescence enhancement as well as chirality ind...
Highly enantioselective selenocyclization reactions are promoted by the combination of a new chiral squaramide catalyst, a mineral acid, and an achiral Lewis base. Mechanistic studies reveal that the enantioselectivity originates from the dynamic kinetic resolution of seleniranium ions through anion-binding catalysis.
Enantioselective recognition of amino acids was achieved by using a highly ordered chiral assembly of achiral porphyrin on a chiral molecular gel. Exceptionally high enantioselectivity was observed for histidine derivatives by monitoring the CD patterns and fluorescence quenching, K(SV) (l): 26.3 × 10(3) M(-1); K(SV)(D)-enantiomer: 7.03 × 10(3) M(-1).
A highly enantioselective hydrogenation of enamides catalyzed by a dual chiral-achiral acid system was developed. By employing a substoichiometric amount of a chiral phosphoric acid and acetic acid, catalyst loadings as low as 1 mol % of the chiral catalyst were sufficient to provide excellent yield and enantioselectivity of the reduction product.
A pyrrole end-capped bipyridyl ligand incorporating a chiral handle exhibited high solid-state emission when compared to the achiral analogue 1b and to the racemic molecule 1c which allowed the design of a reusable fluorescent probe for the selective detection of Zn2+ under aqueous conditions.
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