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The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
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Updated: Sep 20, 2025

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of &#945;-Imino &#947;-Lactones and Alkylidene Pyrazolones
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Chiral-at-Tungsten Dioxo Complexes─A Computational Study on Inhibiting Racemization.

George Dhimba1, Alfred Muller1, Koop Lammertsma1,2

  • 1Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg 2006, South Africa.

Inorganic Chemistry
|May 29, 2025
PubMed
Summary
This summary is machine-generated.

Chiral tungsten complexes racemize through four pathways. Steric bulk influences pathways, with the Dhimba-Muller-Lammertsma (DML) twist being the most favored for potential asymmetric catalysis applications.

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Area of Science:

  • Inorganic Chemistry
  • Computational Chemistry
  • Catalysis

Background:

  • Chiral tungsten complexes are of interest for asymmetric catalysis.
  • Understanding racemization pathways is crucial for designing stable chiral catalysts.

Purpose of the Study:

  • To investigate the racemization pathways of chiral cis-WO2(acac)2 and cis-WO2(nacnac)2 complexes.
  • To assess the impact of steric hindrance on racemization barriers.
  • To identify preferred racemization mechanisms for potential catalytic applications.

Main Methods:

  • Density Functional Theory (DFT) calculations were employed.
  • The ωB97X-D/6-311+G(2d,f) level of theory with LANL2DZ for tungsten was used.
  • Acetonitrile solvent effects were included in the calculations.

Main Results:

  • Four racemization pathways were identified for the studied tungsten complexes.
  • Steric congestion from N-Me and N-Ph substitutions significantly increased racemization barriers.
  • The Dhimba-Muller-Lammertsma (DML) twist mechanism was found to be preferred over Conte-Hippler (CH), Bailar (B), and Ray-Dutt (RD) twists.
  • A high ΔG barrier of 25.7 kcal/mol was calculated for the favored DML pathway in WO2(nacnac)2Ph4.

Conclusions:

  • The DML twist is the dominant racemization pathway for these chiral tungsten complexes.
  • Substituted cis-WO2(nacnac)2 complexes, particularly WO2(nacnac)2Ph4, exhibit high racemization barriers.
  • These findings suggest that chiral tungsten complexes with appropriate steric bulk are viable candidates for asymmetric catalysis.