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"Shao, Hua"
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Advances in asymmetric organocatalysis over the last 10 years
Beyond esoteric interest, organocatalysis has now become one major pillar of asymmetric catalysis. Here, we discuss how new activation modes are conquering challenging stereoselective transformations and the recent integration of organocatalysis with emerging photo- and electrocatalysis, as well as artificial intelligence.
Organocatalysis has become a major pillar of (asymmetric) catalysis. Here, the authors discuss recent trends in organocatalytic activation modes for challenging stereoselective transformations and the emerging integration with other fields, such as photoredox catalysis and electrosynthesis.
Journal Article
Asymmetric phosphoric acid–catalyzed four-component Ugi reaction
The nearly 60-year-old Ugi reaction is a remarkably efficient means of linking together four molecular building blocks: an aldehyde, an amine, a carboxylic acid, and an isocyanide. Because each component is independently tunable, the reaction is especially well suited to the assembly of diverse compound libraries. However, stereoselectivity has been a challenge. Zhang et al. now show that chiral phosphoric acids can catalyze the four-component coupling with high enantioselectivity (see the Perspective by Riva). Theory suggests that a hydrogen-bonded complex involving the phosphoric acid and carboxylic acid sets the stereochemistry for isocyanide attack on an imine intermediate. Science , this issue p. eaas8707 ; see also p. 1072 A chiral phosphoric acid derivative enantioselectively links together an aldehyde, a carboxylic acid, an amine, and an isocyanide. The Ugi reaction constructs α-acylaminoamide compounds by combining an aldehyde or ketone, an amine, a carboxylic acid, and an isocyanide in a single flask. Its appealing features include inherent atom and step economy together with the potential to generate products of broad structural diversity. However, control of the stereochemistry in this reaction has proven to be a formidable challenge. We describe an efficient enantioselective four-component Ugi reaction catalyzed by a chiral phosphoric acid derivative that delivers more than 80 α-acylaminoamides in good to excellent enantiomeric excess. Experimental and computational studies establish the reaction mechanism and origins of stereoselectivity.
Journal Article
gamma-UPC: automated generation of exclusive photon-photon processes in ultraperipheral proton and nuclear collisions with varying form factors
A
bstract
The automated generation of arbitrary exclusive final states produced via photon fusion in ultraperipheral high-energy collisions of protons and/or nuclei, A B
→
γγ
A
X
B, is implemented in the M
ad
G
raph
5_
a
MC@NLO and HELAC-O
nia
Monte Carlo codes. Cross sections are calculated in the equivalent photon approximation using γ fluxes derived from electric dipole and charge form factors, and incorporating hadronic survival probabilities. Multiple examples of γγ cross sections computed with this setup, named gamma-UPC, are presented for proton-proton, proton- nucleus, and nucleus-nucleus ultraperipheral collisions (UPCs) at the Large Hadron Collider and Future Circular Collider. Total photon-fusion cross sections for the exclusive production of spin-0, 2 resonances (quarkonia, ditauonium, and Higgs boson; as well as axions and gravitons), and for pairs of particles (J/ψJ/ψ, WW, ZZ, Zγ,
t
t
¯
, HH) are presented. Differential cross sections for exclusive dileptons and light-by-light scattering are compared to LHC data. This development paves the way for the upcoming automatic event generation of any UPC final state with electroweak corrections at next-to-leading-order accuracy and beyond.
Journal Article
Organocatalytic atroposelective construction of axially chiral arylquinones
Atropisomeric biaryl motifs are ubiquitous in chiral catalysts and ligands. Numerous efficient strategies have been developed for the synthesis of axially chiral biaryls. In contrast, the asymmetric construction of
o
-quinone-aryl atropisomers has yet to be realized. Inspired by the rapid progress of the chemistry of biaryls, here we present our initial investigations about the atroposelective construction of axially chiral arylquinones by a bifunctional chiral phosphoric acid-catalyzed asymmetric conjugate addition and central-to-axial chirality conversion. With o-naphthoquinone as both the electrophile and the oxidant, three types of arylation counterparts, namely 2-naphthylamines, 2-naphthols and indoles, are utilized to assemble a series of atropisomeric scaffolds in good yields and excellent enantioselectivities. This approach not only expands the axially chiral library but also offers a route to a class of potential, chiral biomimetic catalysts.
Axially chiral compounds have widespread use in asymmetric catalysis. Here, the authors disclose a highly enantioselective synthesis of axially chiral
o
-naphthoquinones by chiral phosphoric acid catalysis and central-to-axial chirality conversion.
Journal Article
مجمع بيبا السكني
((مجمع بيبا السكني)) رواية تتخذ من موضوع التخفيف من حدة الفقر موضوعا لها، وتركز على \"الأقوياء\" الذين لا يقهرون في تجربة مكافحة الفقر. وتتخذ من مجمع بيبا السكني في إحدى القرى الجبلية الفقيرة في المنطقة السوفيتية المركزية بجيانغشي مسرحا لأحداث الرواية، ومن خلال الماضي والحاضر لأحد المجمعات السكنية وبأسلوب فني تعيد تجسيد معجزة التخفيف من حدة الفقر في تلك المنطقة القديمة بخصائص ومشاعر فريدة. في هذا المجمع السكني الفقير المليء بطابع الهاكا ودفء المشاعر الإنسانية، تستخدم الكاتبة القلم النسائي الدقيق والموهوب والحساس لتنسج للقاريء لوحة فنية لمجموعة من الشخصيات المحبوبة المحترمة، ومن بينهم خه جين هوا وجين تساي فنغ وغيرهم من كوادر مساعدة الفقراء، وشي هاو تساي وشيوي شيو تشن وغيرهم من المستهدفين للتخفيف من حدة الفقر، بالإضافة إلى عم أخرس وعجوز جيوي تسي اللذين يمثلان الجيش الأحمر القديم وأهالى العسكريين.
Book
Phosphoric acid-catalyzed atroposelective construction of axially chiral arylpyrroles
Axially chiral arylpyrroles are key components of pharmaceuticals and natural products as well as chiral catalysts and ligands for asymmetric transformations. However, the catalytic enantioselective construction of optically active arylpyrroles remains a formidable challenge. Here we disclose a highly efficient strategy to access enantioenriched axially chiral arylpyrroles by means of organocatalytic atroposelective desymmetrization and kinetic resolution. Depending on the remote control of chiral catalyst, the arylpyrroles were obtained in high yields and excellent enantioselectivities under mild reaction conditions. This strategy tolerates a wide range of functional groups, providing a facile avenue to approach axially chiral arylpyrroles from simple and readily available starting materials. Selected arylpyrrole products proved to be efficient chiral ligands in asymmetric catalysis and also important precursors for further synthetic transformations into highly functionalized pyrroles with potential bioactivity, especially the axially chiral fully substituted arylpyrroles.
Axially chiral arylpyrroles are structural motifs often found in natural and medicinal products. Here, the authors report the atroposelective synthesis of axially chiral arylpyrrole derivatives, which proved to be efficient chiral ligands for asymmetric catalysis, through desymmetrization and kinetic resolution.
Journal Article