A study of enantioselective syntheses by Sharpless asymmetric oxidation for aryl sulfoxides containing oxygen groups at the ortho position

Advances in asymmetric catalysis have led to enormous progress in the atroposelective synthesis of axially chiral biaryls. Because of the biological importance of indoles, stereogenic axes in aryl-substituted indoles have attracted considerable research attention in recent years. Here we present a summary of recent advances in the atroposelective synthesis of aryl-substituted indoles by dynamic kinetic resolution. While several researchers have developed enantioselective syntheses of 3-arylindoles, N-arylindoles have been much less studied. Accordingly, we have reported a Pictet–Spengler reaction with catalytic and enantioselective control of the axial chirality around the C−N bond of the product. A chiral phosphoric acid induces the cyclization smoothly and with high yields and excellent enantioselectivities. To achieve this high selectivity, an NH group at the ortho position of the N-substituted aromatic ring that interacts favorably with the catalyst is required. Furthermore, when substituted aldehydes are used instead of paraformaldehyde, both the point and axial chiralities can be controlled during the cyclization.

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Enantioselective Syntheses of Flavonoid Diels-Alder Natural Products: A Review

Current Organic Synthesis ◽

10.2174/1570179414666170821120234 ◽

2018 ◽

Vol 15 (2) ◽

pp. 221-229 ◽

Cited By ~ 3

Author(s):

Shah Bakhtiar Nasir ◽

Noorsaadah Abd Rahman ◽

Chin Fei Chee

Keyword(s):

Natural Products ◽

Organic Synthesis ◽

Lewis Acid ◽

Alder Reaction ◽

Diels Alder ◽

Enantioselective Synthesis ◽

Chiral Ligand ◽

Asymmetric Syntheses ◽

Diels Alder Reaction ◽

Enantioselective Syntheses

Background: The Diels-Alder reaction has been widely utilised in the syntheses of biologically important natural products over the years and continues to greatly impact modern synthetic methodology. Recent discovery of chiral organocatalysts, auxiliaries and ligands in organic synthesis has paved the way for their application in Diels-Alder chemistry with the goal to improve efficiency as well as stereochemistry. Objective: The review focuses on asymmetric syntheses of flavonoid Diels-Alder natural products that utilize chiral ligand-Lewis acid complexes through various illustrative examples. Conclusion: It is clear from the review that a significant amount of research has been done investigating various types of catalysts and chiral ligand-Lewis acid complexes for the enantioselective synthesis of flavonoid Diels-Alder natural products. The results have demonstrated improved yield and enantioselectivity. Much emphasis has been placed on the synthesis but important mechanistic work aimed at understanding the enantioselectivity has also been discussed.

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Asymmetric Oxidation of Aromatic Sulfides with Hydrogen Peroxide Catalyzed by Transition Metal Complexes of Polyphenol-Appended .BETA.-Cyclodextrin Derivatives.

NIPPON KAGAKU KAISHI ◽

10.1246/nikkashi.2002.399 ◽

2002 ◽

pp. 399-407

Author(s):

Hidetake SAKURABA ◽

Hiroshi MAEKAWA ◽

Satoshi TAKIZAWA ◽

Sachiko IRIUCHIJIMA ◽

Manami YAMADA

Keyword(s):

Hydrogen Peroxide ◽

Transition Metal ◽

Metal Complexes ◽

Transition Metal Complexes ◽

Cyclodextrin Derivatives ◽

Asymmetric Oxidation ◽

Beta Cyclodextrin

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ChemInform Abstract: Synthesis of New Chiral Ligands Based on Thiophene Derivatives for Use in Catalytic Asymmetric Oxidation of Sulfides.

ChemInform ◽

10.1002/chin.201131024 ◽

2011 ◽

Vol 42 (31) ◽

pp. no-no

Author(s):

Yong-Chul Jeong ◽

Dae-Jun Ahn ◽

Woo-Sun Lee ◽

Seung-Han Lee ◽

Kwang-Hyun Ahn

Keyword(s):

Chiral Ligands ◽

Asymmetric Oxidation ◽

Oxidation Of Sulfides ◽

Thiophene Derivatives ◽

Catalytic Asymmetric

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Tailoring Properties of Resol Resin-Derived Spherical Carbons for Adsorption of Phenol from Aqueous Solution

Molecules ◽

10.3390/molecules26061736 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1736

Author(s):

Karol Sidor ◽

Tomasz Berniak ◽

Piotr Łątka ◽

Anna Rokicińska ◽

Marek Michalik ◽

...

Keyword(s):

Surface Composition ◽

Micropore Volume ◽

Gaseous Ammonia ◽

Poly Vinyl Alcohol ◽

Clear Correlation ◽

Hno3 Solution ◽

Synthesis Conditions ◽

Adsorption Of Nitrogen ◽

Oxygen Groups ◽

Size Of Particles

The polycondensation of resorcinol and formaldehyde in a water–ethanol mixture using the adapted Stöber method was used to obtain resol resins. An optimization of synthesis conditions and the use of an appropriate stabilizer (e.g., poly(vinyl alcohol)) resulted in spherical grains. The resins were carbonized in the temperature range of 600–1050 °C and then chemically activated in an aqueous HNO3 solution, gaseous ammonia, or by an oxidation–reduction cycle (soaking in a HNO3 solution followed by treatment with NH3). The obtained carbons were characterized by XRD, the low-temperature adsorption of nitrogen, SEM, TGA, and XPS in order to determine degree of graphitization, porosity, shape and size of particles, and surface composition, respectively. Finally, the materials were tested in phenol adsorption. The pseudo-second order model perfectly described the adsorption kinetics. A clear correlation between the micropore volume and the adsorption capacity was found. The content of graphite domains also had a positive effect on the adsorption properties. On the other hand, the presence of heteroatoms, especially oxygen groups, resulted in the clogging of the pores and a decrease in the amount of adsorbed phenol.

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Fluorescent Orthopalladated Complexes of 4-Aryliden-5(4H)-Oxazolones from the Kaede Protein: Synthesis and Characterization

Molecules ◽

10.3390/molecules26051238 ◽

2021 ◽

Vol 26 (5) ◽

pp. 1238

Author(s):

Eduardo Laga ◽

David Dalmau ◽

Sofía Arregui ◽

Olga Crespo ◽

Ana I. Jimenez ◽

...

Keyword(s):

Intramolecular Interactions ◽

Ortho Position ◽

Fluorescent Properties ◽

Ancillary Ligands ◽

X Ray ◽

Mononuclear Complexes ◽

Fluorescence Measurements ◽

Anionic Ligands ◽

Order Of Magnitude

The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4H)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the ortho carbon of the arylidene ring. Two different 4-((Z)-arylidene)-2-((E)-styryl)-5(4H)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring (1a OMe; 1b F), were used as starting materials. Oxazolones 1a and 1b were reacted with Pd(OAc)2 to give the corresponding dinuclear orthometalated palladium derivates 2a and 2b by regioselective C–H activation of the ortho-position of the arylidene ring. Reaction of 2a (2b) with LiCl promoted the metathesis of the bridging carboxylate by chloride ligands to afford dinuclear 3a (3b). Mononuclear complexes containing the orthopalladated oxazolone and a variety of ancillary ligands (acetylacetonate (4a, 4b), hydroxyquinolinate (5a), aminoquinoline (6a), bipyridine (7a), phenanthroline (8a)) were prepared from 3a or 3b through metathesis of anionic ligands or substitution of neutral weakly bonded ligands. All species were fully characterized and the X-ray determination of the molecular structure of 7a was carried out. This structure has strongly distorted ligands due to intramolecular interactions. Fluorescence measurements showed an increase in the quantum yield (QY) by up to one order of magnitude on comparing the free oxazolone (QY < 1%) with the palladated oxazolone (QY = 12% for 6a). This fact shows that the coordination of the oxazolone to the palladium efficiently suppresses the hula-twist deactivation pathway.

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Selective activation of C H bond of phenol in ortho-position into C OH bond in a two-phase system

Catalysis Communications ◽

10.1016/j.catcom.2020.106277 ◽

2021 ◽

Vol 150 ◽

pp. 106277

Author(s):

Ke Zheng ◽

Song Shi ◽

Hongchuan Xin ◽

Jin Gao ◽

Zengjian An

Keyword(s):

Phase System ◽

Ortho Position ◽

Selective Activation ◽

Two Phase

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Design and synthesis of herboxidiene derivatives that potently inhibit in vitro splicing

Organic & Biomolecular Chemistry ◽

10.1039/d0ob02532a ◽

2021 ◽

Vol 19 (6) ◽

pp. 1365-1377

Author(s):

Arun K. Ghosh ◽

Srinivasa Rao Allu ◽

Guddeti Chandrashekar Reddy ◽

Adriana Gamboa Lopez ◽

Patricia Mendez ◽

...

Keyword(s):

Biological Evaluation ◽

Design And Synthesis ◽

In Vitro Splicing ◽

Enantioselective Syntheses ◽

Derivatives Of

Enantioselective syntheses of C-6 modified derivatives of herboxidiene and their biological evaluation in splicing inhibitory assay.

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Thermogravimetric Analysis (TGA) of Graphene Materials: Effect of Particle Size of Graphene, Graphene Oxide and Graphite on Thermal Parameters

C – Journal of Carbon Research ◽

10.3390/c7020041 ◽

2021 ◽

Vol 7 (2) ◽

pp. 41

Author(s):

Farzaneh Farivar ◽

Pei Lay Yap ◽

Ramesh Udayashankar Karunagaran ◽

Dusan Losic

Keyword(s):

Particle Size ◽

Quality Control ◽

Graphene Oxide ◽

Thermogravimetric Analysis ◽

Low Cost ◽

Thermal Parameters ◽

Carbon Decomposition ◽

Size Number ◽

Carbon Combustion ◽

Oxygen Groups

Thermogravimetric analysis (TGA) has been recognized as a simple and reliable analytical tool for characterization of industrially manufactured graphene powders. Thermal properties of graphene are dependent on many parameters such as particle size, number of layers, defects and presence of oxygen groups to improve the reliability of this method for quality control of graphene materials, therefore it is important to explore the influence of these parameters. This paper presents a comprehensive TGA study to determine the influence of different particle size of the three key materials including graphene, graphene oxide and graphite on their thermal parameters such as carbon decomposition range and its temperature of maximum mass change rate (Tmax). Results showed that Tmax values derived from the TGA-DTG carbon combustion peaks of these materials increasing from GO (558–616 °C), to graphene (659–713 °C) and followed by graphite (841–949 °C) The Tmax values derived from their respective DTG carbon combustion peaks increased as their particle size increased (28.6–120.2 µm for GO, 7.6–73.4 for graphene and 24.2–148.8 µm for graphite). The linear relationship between the Tmax values and the particle size of graphene and their key impurities (graphite and GO) confirmed in this study endows the use of TGA technique with more confidence to evaluate bulk graphene-related materials (GRMs) at low-cost, rapid, reliable and simple diagnostic tool for improved quality control of industrially manufactured GRMs including detection of “fake” graphene.

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High flow oxygen and risk of mortality in patients with a suspected acute coronary syndrome: pragmatic, cluster randomised, crossover trial

BMJ ◽

10.1136/bmj.n355 ◽

2021 ◽

pp. n355

Author(s):

Ralph A H Stewart ◽

Peter Jones ◽

Bridget Dicker ◽

Yannan Jiang ◽

Tony Smith ◽

...

Keyword(s):

Acute Coronary Syndrome ◽

New Zealand ◽

Crossover Trial ◽

High Flow ◽

Low Oxygen ◽

Coronary Syndrome ◽

Cluster Randomised ◽

Geographical Regions ◽

High Flow Oxygen ◽

Oxygen Groups

Abstract Objective To determine the association between high flow supplementary oxygen and 30 day mortality in patients presenting with a suspected acute coronary syndrome (ACS). Design Pragmatic, cluster randomised, crossover trial. Setting Four geographical regions in New Zealand. Participants 40 872 patients with suspected or confirmed ACS included in the All New Zealand Acute Coronary Syndrome Quality Improvement registry or ambulance ACS pathway during the study periods. 20 304 patients were managed using the high oxygen protocol and 20 568 were managed using the low oxygen protocol. Final diagnosis of ST elevation myocardial infarction (STEMI) and non-STEMI were determined from the registry and ICD-10 discharge codes. Interventions The four geographical regions were randomly allocated to each of two oxygen protocols in six month blocks over two years. The high oxygen protocol recommended oxygen at 6-8 L/min by face mask for ischaemic symptoms or electrocardiographic changes, irrespective of the transcapillary oxygen saturation (SpO 2 ). The low oxygen protocol recommended oxygen only if SpO 2 was less than 90%, with a target SpO 2 of less than 95%. Main outcome measure 30 day all cause mortality determined from linkage to administrative data. Results Personal and clinical characteristics of patients managed under both oxygen protocols were well matched. For patients with suspected ACS, 30 day mortality for the high and low oxygen groups was 613 (3.0%) and 642 (3.1%), respectively (odds ratio 0.97, 95% confidence interval 0.86 to 1.08). For 4159 (10%) patients with STEMI, 30 day mortality for the high and low oxygen groups was 8.8% (n=178) and 10.6% (n=225), respectively (0.81, 0.66 to 1.00) and for 10 218 (25%) patients with non-STEMI was 3.6% (n=187) and 3.5% (n=176), respectively (1.05, 0.85 to 1.29). Conclusion In a large patient cohort presenting with suspected ACS, high flow oxygen was not associated with an increase or decrease in 30 day mortality. Trial registration ANZ Clinical Trials ACTRN12616000461493.

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