alkaloid derivatives as Brønsted base catalysts have attracted considerable attention in the field of asymmetric catalysis. However, their potential application as chiral solvating agents has not been described. In this research, we investigated the use of the alkaloid dimer, namely, (DHQ)PHAL, as a chiral solvating agent for discerning various mandelic acid derivatives through H NMR spectroscopy. The addition of catalytic amounts of DMAP facilitated this process. Our experimental results demonstrate that dimeric (DHQ)PHAL exhibits remarkable chiral discrimination properties regarding the diagnostic split protons of H NMR signals (including 24 examples, up to 0.321 ppm). Furthermore, it serves as an excellent chiral discriminating agent and provides good resolution for racemic chiral phosphoric acid as determined by P NMR spectroscopy. The quality of enantiodifferentiation has also been evaluated by means of the parameter "resolution ()". Significantly, this class of CSAs based on (alkaloid)linker systems with an azaaromatic linker can be directly employed, which is commercially available in an enantiopure form at very low cost and exhibits promising potential in determining the enantiopurity of α-hydroxy acids by chemoselective and biocatalytic reactions.
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http://dx.doi.org/10.1021/acs.analchem.4c00053 | DOI Listing |
Org Biomol Chem
December 2024
Department of Chemistry, Bogazici University, Bebek, Istanbul 34342, Turkey.
Aldol reactions are one of the most fundamental organic reactions involving the formation of carbon-carbon bonds that are commonly used in the synthesis of complex molecules through the condensation of an enol or enolate with a carbonyl group. The aldol reaction of thiohydantoin derivatives with benzaldehyde starts with hydrogen removal from C5 by lithium diisopropylamide (LDA) to form the enolate. Benzaldehyde adds to the enolate either at the less or more hindered site.
View Article and Find Full Text PDFPhys Chem Chem Phys
December 2024
Department of Chemistry, Visva-Bharati University, Santiniketan, West Bengal-731235, India.
First-principles analyses were performed for understanding the mechanistic details of Fe-catalysed asymmetric hydrogenation of alkenes in the presence of silane that has recently been experimentally realized. The catalytic hydrogenation is expected to proceed through initial hydride transfer from Fe-H to the CC bond of alkene, followed by σ-bond metathesis of hydrosilane to afford a chiral alkane product and an iron silyl species, which then reacts with H to regenerate the iron hydride species another σ-bond metathesis. The mechanistic details and the origin of the regioselectivity and stereoselectivity of these reactions are understood on the basis of detailed potential energy surface analysis, charge transfer and noncovalent interactions involved therein, strain energy and isodesmic studies in the solvated stage.
View Article and Find Full Text PDFJ Mol Model
December 2024
College of Chemistry and Material Science, Shandong Agricultural University, Taian, Shandong, 271018, People's Republic of China.
Context: Nickel-catalyzed hydroamination of dienes with phenylmethanamines was studied theoretically to investigate reaction mechanism. These calculated results revealed that Ni-catalyzed hydroamination began with the O - H bond activation of trifluoroethanol, including three important elementary steps: the ligand-to-ligand hydrogen migration, the nucleophilic attack of phenylmethanamine, and hydrogen migration. The nucleophilic attack of phenylmethanamine was the rate-determining step, and the branched product of 3,4-addition with (S)-chirality was the most dominant.
View Article and Find Full Text PDFChem Sci
December 2024
CNRS, LCC (Laboratoire de Chimie de Coordination), Université de Toulouse, UPS, INPT 205 Route de Narbonne, BP 44099, F-31077 Toulouse Cedex 4 France +33-561553003 +33-561333174.
Catalytic asymmetric hydrogenation of ketones is an important approach to prepare valuable chiral alcohols. Understanding how transition metals promote these reactions is key to the rational design of more active, selective and sustainable catalysts. A highly unusual mechanism for asymmetric hydrogenation of acetophenone catalysed by an anionic Ir hydride system, including a strong counterion dependence on catalyst activity, is explored and rationalised here.
View Article and Find Full Text PDFJ Am Chem Soc
November 2024
Department of Chemistry and Chemical Biology, TU Dortmund University, Otto Hahn Str. 6, 44227 Dortmund, Germany.
A family of Pd cages prepared from ligands based on an axially chiral diamino-[1,1'-biazulene] motif (serving as a unique azulene-based surrogate of the ubiquitous BINOL moiety) is reported. We show that preparing a cage starting from the racemate of a shorter bis-monodentate ligand derivative, equipped with pyridine donor groups, leads to integrative ("social") chiral self-sorting, exclusively yielding the product, but only in a selection of solvents. This phenomenon is driven by individual solvent molecules acting as hydrogen bonding tethers between the amino groups of neighboring ligands, thereby locking the final coordination cage in a single isomeric form.
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