Browse
Submit Data
Databases
API
Help

Dataset Information

13 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Photochemical Deracemization of Allenes and Subsequent Chirality Transfer.

ABSTRACT: Trisubstituted allenes with a 3-(1'-alkenylidene)-pyrrolidin-2-one motif were successfully deracemized (13 examples, 86-98?% ee) employing visible light (?=420?nm) and a chiral triplet sensitizer as the catalyst (2.5?mol?%). The photocatalyst likely operates by selective recognition of one allene enantiomer via hydrogen bonds and by a triplet-sensitized racemization process. Even a tetrasubstituted allene (45?% ee) and a seven-membered 3-(1'-alkenylidene)-azepan-2-one (62?% ee) could be enantiomerically enriched under the chosen conditions. It was shown that the axial chirality of the allenes can be converted into point chirality by a Diels-Alder (94-97?% ee) or a bromination reaction (91?% ee). Ring opening of the five-membered pyrrolidin-2-one was achieved without significantly compromising the integrity of the chirality axis (92?% ee).

SUBMITTER: Plaza M

PROVIDER: S-EPMC7537568 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Photochemical Deracemization of Allenes and Subsequent Chirality Transfer.

Plaza Manuel M Jandl Christian C Bach Thorsten T

Angewandte Chemie (International ed. in English) 20200602 31

Trisubstituted allenes with a 3-(1'-alkenylidene)-pyrrolidin-2-one motif were successfully deracemized (13 examples, 86-98 % ee) employing visible light (λ=420 nm) and a chiral triplet sensitizer as the catalyst (2.5 mol %). The photocatalyst likely operates by selective recognition of one allene enantiomer via hydrogen bonds and by a triplet-sensitized racemization process. Even a tetrasubstituted allene (45 % ee) and a seven-membered 3-(1'-alkenylidene)-azepan-2-one (62 % ee) could be enantiom ...[more]

PMID: 32390291

Similar Datasets

Enantiodivergent Synthesis of Allenes by Point-to-Axial Chirality Transfer.

Project description:An enantiodivergent method for the synthesis of multiply substituted allenes is described. Highly enantioenriched, point-chiral boronic esters were synthesized by homologation of ?-seleno alkenyl boronic esters with lithiated carbamates and eliminated to form axially chiral allene products. By employing either oxidative or alkylative conditions, both syn and anti elimination could be achieved with complete stereospecificity. The process enables the synthesis of either M or P?allenes from a single isomer of a point-chiral precursor and can be employed for the enantioselective assembly of di-, tri-, and tetrasubstituted allenes.

| S-EPMC6033179 | biostudies-literature

Chirality Transfer in Gold(I)-Catalysed Hydroalkoxylation of 1,3-Disubstituted Allenes.

Project description:Gold(I)-catalysed intermolecular hydroalkoxylation of enantioenriched 1,3-disubstituted allenes was previously reported to occur with poor chirality transfer due to rapid allene racemisation. The first intermolecular hydroalkoxylation of allenes with efficient chirality transfer is reported here, exploiting conditions that suppress allene racemisation. A full substrate scope study reveals that excellent regio- and stereoselectivities are achieved when a ?-withdrawing substituent is present.

| S-EPMC5215423 | biostudies-literature

Catalytic enantioselective construction of axial chirality in 1,3-disubstituted allenes.

Project description:Metal-catalyzed enantioselective construction of the loosening axial allene chirality spreading over three carbon atoms using a chiral ligand is still a significant challenge. In the literature, steric effect of the substrates is the major strategy applied for such a purpose. Herein, we present a general palladium-catalyzed asymmetrization of readily available racemic 2,3-allenylic carbonates with different types of non-substituted and 2-substituted malonates using (R)-(-)-DTBM-SEGPHOS as the preferred ligand to afford 1,3-disubstituted chiral allenes with 90~96% ee. This protocol has been applied to the first enantioselective synthesis of natural product, (R)-traumatic lactone. Control experiments showed that in addition to the chiral ligand, conducting this transformation via Procedure C, which excludes the extensive prior coordination of the allene unit in the starting allene with Pd forming a species without the influence of the chiral ligand, is crucial for the observed high enantioselectivity.

| S-EPMC6355870 | biostudies-other

Light-driven deracemization enabled by excited-state electron transfer.

Project description:Deracemization is an attractive strategy for asymmetric synthesis, but intrinsic energetic challenges have limited its development. Here, we report a deracemization method in which amine derivatives undergo spontaneous optical enrichment upon exposure to visible light in the presence of three distinct molecular catalysts. Initiated by an excited-state iridium chromophore, this reaction proceeds through a sequence of favorable electron, proton, and hydrogen-atom transfer steps that serve to break and reform a stereogenic C-H bond. The enantioselectivity in these reactions is jointly determined by two independent stereoselective steps that occur in sequence within the catalytic cycle, giving rise to a composite selectivity that is higher than that of either step individually. These reactions represent a distinct approach to creating out-of-equilibrium product distributions between substrate enantiomers using excited-state redox events.

| S-EPMC6939311 | biostudies-literature

Stoichiometric Photochemical Carbene Transfer by Bamford-Stevens Reaction.

Project description:The photolysis of diazoalkanes is a timely strategy to conduct carbene-transfer reactions under mild and metal-free reaction conditions, and has developed as an important alternative to conventional metal-catalyzed carbene-transfer reactions. One of the major limitations lies within the rapidly occurring side reaction of the carbene intermediate with remaining diazoalkane molecules that result in the use of an excess of the reaction partner and thus impacts on the reaction efficiency. Herein, we describe a protocol that takes advantage of the in situ generation of donor-acceptor diazoalkanes by Bamford-Stevens reaction. Following this strategy, the concentration of the diazoalkane reaction partner can be minimized to reduce unwanted side reactions and to now conduct photochemical carbene transfer reactions under stoichiometric reaction conditions. We have explored this approach in the C-H and N-H functionalization and cyclopropanation reaction of N-heterocycles and could demonstrate the applicability of this method in 51?examples.

| S-EPMC7065054 | biostudies-literature

Chirality-assisted lateral momentum transfer for bidirectional enantioselective separation.

Project description:Lateral optical forces induced by linearly polarized laser beams have been predicted to deflect dipolar particles with opposite chiralities toward opposite transversal directions. These "chirality-dependent" forces can offer new possibilities for passive all-optical enantioselective sorting of chiral particles, which is essential to the nanoscience and drug industries. However, previous chiral sorting experiments focused on large particles with diameters in the geometrical-optics regime. Here, we demonstrate, for the first time, the robust sorting of Mie (size ~ wavelength) chiral particles with different handedness at an air-water interface using optical lateral forces induced by a single linearly polarized laser beam. The nontrivial physical interactions underlying these chirality-dependent forces distinctly differ from those predicted for dipolar or geometrical-optics particles. The lateral forces emerge from a complex interplay between the light polarization, lateral momentum enhancement, and out-of-plane light refraction at the particle-water interface. The sign of the lateral force could be reversed by changing the particle size, incident angle, and polarization of the obliquely incident light.

| S-EPMC7160209 | biostudies-literature

Intramolecular Chirality Transfer [2 + 2] Cycloadditions of Allenoates and Alkenes.

Project description:Intramolecular chirality transfer [2 + 2] cycloaddition of enantiomerically enriched allenoates and alkenes is presented. The use of a chiral catalyst was found to be critical to achieve high levels of diastereoselectivity compared to use of an achiral catalyst. The method developed leads to highly substituted cyclobutanes that would be difficult to prepare by alternative methods.

| S-EPMC5606144 | biostudies-literature

Hierarchical chirality transfer in the growth of Towel Gourd tendrils.

Project description:Chirality plays a significant role in the physical properties and biological functions of many biological materials, e.g., climbing tendrils and twisted leaves, which exhibit chiral growth. However, the mechanisms underlying the chiral growth of biological materials remain unclear. In this paper, we investigate how the Towel Gourd tendrils achieve their chiral growth. Our experiments reveal that the tendrils have a hierarchy of chirality, which transfers from the lower levels to the higher. The change in the helical angle of cellulose fibrils at the subcellular level induces an intrinsic torsion of tendrils, leading to the formation of the helical morphology of tendril filaments. A chirality transfer model is presented to elucidate the chiral growth of tendrils. This present study may help understand various chiral phenomena observed in biological materials. It also suggests that chirality transfer can be utilized in the development of hierarchically chiral materials having unique properties.

| S-EPMC3813933 | biostudies-literature

Gold-Catalyzed Synthesis of Chiral Cyclopentadienyl Esters via Chirality Transfer.

Project description:Efficient access to chiral cyclopentadienyl esters from readily accessible chiral enynyl ester substrates is developed. Typically high levels of chirality transfer realized in this homogeneous gold catalysis are attributed to the intermediacy of a chiral bent allene gold complex. Cyclopentadienyl esters can be prepared in good yields and with excellent enantiomeric excesses. The synthetic utilities of the chiral cyclopentadienyl esters are demonstrated by the Diels-Alder reactions, fluorination, alkylation, and epoxidation without any notable erosion of enantiopurity.

| S-EPMC8623356 | biostudies-literature

Spontaneous transfer of chirality in an atropisomerically enriched two-axis system.

Project description:One of the most well-recognized stereogenic elements in a chiral molecule is an sp(3)-hybridized carbon atom that is connected to four different substituents. Axes of chirality can also exist about bonds with hindered barriers of rotation; molecules containing such axes are known as atropisomers. Understanding the dynamics of these systems can be useful, for example, in the design of single-atropisomer drugs or molecular switches and motors. For molecules that exhibit a single axis of chirality, rotation about that axis leads to racemization as the system reaches equilibrium. Here we report a two-axis system for which an enantioselective reaction produces four stereoisomers (two enantiomeric pairs): following a catalytic asymmetric transformation, we observe a kinetically controlled product distribution that is perturbed from the system's equilibrium position. As the system undergoes isomerization, one of the diastereomeric pairs drifts spontaneously to a higher enantiomeric ratio. In a compensatory manner, the enantiomeric ratio of the other diastereomeric pair decreases. These observations are made for a class of unsymmetrical amides that exhibits two asymmetric axes--one axis is defined through a benzamide substructure, and the other axis is associated with differentially N,N-disubstituted amides. The stereodynamics of these substrates provides an opportunity to observe a curious interplay of kinetics and thermodynamics intrinsic to a system of stereoisomers that is constrained to a situation of partial equilibrium.

| S-EPMC4008667 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data