An official website of the United States government
Abstract Acyclic ketone‐derived oxocarbenium ions are involved as intermediates in numerous reactions that provide valuable products, however, they have thus far eluded efforts aimed at asymmetric catalysis. We report that a readily accessible chiral carboxylic acid catalyst exerts control over asymmetric cyclizations of acyclic ketone‐derived trisubstituted oxocarbenium ions, thereby providing access to highly enantioenriched dihydropyran products containing a tetrasubstituted stereogenic center. The high acidity of the carboxylic acid catalyst, which exceeds that of the well‐known chiral phosphoric acid catalyst TRIP, is largely derived from stabilization of the carboxylate conjugate base through intramolecular anion‐binding to a thiourea site.
more »
« less
Combinatorial Ligand Assisted Simultaneous Control of Axial and Central Chirality in Highly Stereoselective C−H Allylation
Abstract The significance of stereoselective C−H bond functionalization thrives on its direct application potential to pharmaceuticals or complex chiral molecule synthesis. Complication arises when there are multiple stereogenic elements such as a center and an axis of chirality to control. Over the years cooperative assistance of multiple chiral ligands has been applied to control only chiral centers. In this work, we harness the essence of cooperative ligand approach to control two different stereogenic elements in the same molecule by atroposelective allylation to synthesize axially chiral biaryls from its racemic precursor. The crucial roles played by chiral phosphoric acid and chiral amino acid ligand in concert helped us to obtain one major stereoisomer out of four distinct possibilities.
more »
« less
- Award ID(s):
- 2029932
- PAR ID:
- 10553791
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 63
- Issue:
- 2
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Acyclic ketone‐derived oxocarbenium ions are involved as intermediates in numerous reactions that provide valuable products, however, they have thus far eluded efforts aimed at asymmetric catalysis. We report that a readily accessible chiral carboxylic acid catalyst exerts control over asymmetric cyclizations of acyclic ketone‐derived trisubstituted oxocarbenium ions, thereby providing access to highly enantioenriched dihydropyran products containing a tetrasubstituted stereogenic center. The high acidity of the carboxylic acid catalyst, which exceeds that of the well‐known chiral phosphoric acid catalyst TRIP, is largely derived from stabilization of the carboxylate conjugate base through intramolecular anion‐binding to a thiourea site.more » « less
-
Abstract A gold(I)‐catalyzed enantioselective dearomatization is achieved via metal‐chiral ligand cooperation. A new and divergent synthesis of chiral bifunctional binaphthyl‐2‐ylphosphines is developed to allow rapid access to these ligands, which in turn facilitate the application of this chemistry to a broad substrate scope including 1‐naphthols, 2‐naphthols, and phenols. Enantiomeric excesses up to 98 % are achieved via selective acceleration of one enantiomer formation enabled by hydrogen bonding between substrate and ligand remote basic group. DFT calculations lend support to the cooperative catalysis and substantiate the reaction stereochemical outcomes.more » « less
-
null (Ed.)Cluster complexes have attracted interest for decades due to their promise of drawing analogies to metallic surfaces and metalloenzyme active sites, but only recently have chemists started to develop ligand scaffolds that are specifically designed to support multinuclear transition metal cores. Such ligands not only hold multiple metal centers in close proximity but also allow for fine-tuning of their electronic structures and surrounding steric environments. This Feature Article highlights ligand designs that allow for cooperative small molecule activation at cluster complexes, with a particular focus on complexes that contain metal–metal bonds. Two useful ligand-design elements have emerged from this work: a degree of geometric flexibility, which allows for novel small molecule activation modes, and the use of redox-active ligands to provide electronic flexibility to the cluster core. The authors have incorporated these factors into a unique class of dinucleating macrocycles ( n PDI 2 ). Redox-active fragments in n PDI 2 mimic the weak-overlap covalent bonding that is characteristic of M–M interactions, and aliphatic linkers in the ligand backbone provide geometric flexibility, allowing for interconversion between a range of geometries as the dinuclear core responds to the requirements of various small molecule substrates. The union of these design elements appears to be a powerful combination for analogizing critical aspects of heterogeneous and metalloenzyme catalysts.more » « less
-
Abstract P-Stereogenic secondary phosphine oxides [SPOs, RR′P(O)H], valuable ligands for metal complexes in asymmetric catalysis, are also building blocks for other chiral phosphorus derivatives. This short review summarizes methods used for asymmetric synthesis of P-stereogenic SPOs. 1 Introduction 2 Configurational Stability of P-Stereogenic SPOs 3 Classical Resolution, HPLC Separation, and Dynamic Resolution 4 Synthesis via Chiral Auxiliaries 5 Kinetic Resolution 6 Conclusions and Outlookmore » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/anie.202310112
