Can enantiomer ligands produce structurally distinct homochiral MOFs?

CrystEngComm ◽  
2015 ◽  
Vol 17 (43) ◽  
pp. 8202-8206 ◽  
Author(s):  
Mrigendra Dubey ◽  
Ashish Kumar ◽  
Vishal M. Dhavale ◽  
Sreekumar Kurungot ◽  
Daya Shankar Pandey
Keyword(s):  
Proton Conductance ◽  
Analogous Reaction ◽  
Reaction Conditions

Here, we report the synthesis, characterization and proton conductance study of two structurally distinct homochiral MOFs [Cu1.5(H2Ll-leu)(Ac)H2O]n·3H2O (1) and [Cu1.5(H2Ld-leu)H2O]n·10H2O (2) obtained from the l/d-leucine derived enantiomer ligands and Cu(Ac)2·H2O in 1 : 1 ratio under analogous reaction conditions.

Electrochemical oxidation of 2-furylacetic acid derivatives

1980 ◽  
Vol 45 (5) ◽  
pp. 1361-1365 ◽  
Author(s):  
Miroslav Janda ◽  
Jan Šrogl ◽  
Eva Körblová ◽  
Ivan Stibor
Keyword(s):  
Electrochemical Oxidation ◽  
Analogous Reaction ◽  
Reaction Conditions

Depanding on reaction conditions, the electrochemical methoxylation of 2-furylacetonitrile (I) afforded either (2,5-dimethoxy-2,5-dihydro-2-furyl)acetonitrile (V) or (5-methoxy-2,5-dihydro-2-furfurylidene)acetonitrile (VIII). Analogous reaction of methyl 2-furylacetate (II) gave either methyl (2,5-dimethoxy-2,5-dihydro-2-furyl)acetate (VI) or methyl (5-methoxy-2,5-dihydro-2-furfurylidene)acetate (IX). The electrochemical ethoxylation of ethyl 2-furylacetate afforded- among other products - also γ-lactone of ethyl 3-hydroxy-2,4-hexadienedioate (X).

Neue Sesquisulfide der Lanthanoide im U2S3-Typ: Tb2S3 und Dy2S3/New U2S3-Type Sesquisulfides of the Lanthanides: Tb2S3 and Dy2S3

1992 ◽  
Vol 47 (1) ◽  
pp. 45-50 ◽  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Type Structure ◽  
Crystal Data ◽  
Analogous Reaction ◽  
Reaction Conditions

New sesquisulfides of the lanthanides with the U2S3-type structure (M2S3, M = Tb and Dy) were prepared through the oxidation of TbClH0,67 and DyCl2, respectively, with appropriate amounts of sulfur in the presence of NaCl fluxes in silica protected sealed tantalum containers at 850 °C for at least seven days. The preparation from the elements (2M + 3S; M = Tb and Dy) under otherwise analogous reaction conditions and temperatures was also successful when equimolar fluxes of NaCl were applied. The crystal structure was determined from single crystal data for Tb2S3 and Dy2S3, both crystallizing with the U2S3-type structure (orthorhombic, Pnma, Z = 4; Tb2S3: a = 1067.87(8), b = 388.06(4), c = 1049.07(7) pm ; Dy2S3: a = 1062.45(7), b = 386.59(4), c = 1044.36(8) pm) when prepared under the above-mentioned conditions.

Attempts to Mimic Key Bond-Forming Events Associated with the Proposed Biogenesis of the Pentacyclic Lamellarins

2008 ◽  
Vol 61 (2) ◽  
pp. 80 ◽  
Author(s):  
Lorraine C. Axford ◽  
Kate E. Holden ◽  
Katrin Hasse ◽  
Martin G. Banwell ◽  
Wolfgang Steglich ◽  
...  
Keyword(s):  
Carboxy Group ◽  
Pyrrole Ring ◽  
Lactone Ring ◽  
Polymeric Materials ◽  
Isoquinoline Alkaloid ◽  
Oxidative Cyclization ◽  
Analogous Reaction ◽  
Cyclization Reactions ◽  
Reaction Conditions ◽  
Bond Forming

The pyrrole-tethered veratroles 16 and 27 each engage in PIFA-induced oxidative cyclization reactions to give compounds 22 and 29, respectively, which incorporate a key tricyclic fragment associated with the title natural products. In contrast, the corresponding catechols 11 and 12 only produce polymeric materials on subjection to analogous reaction conditions. Efforts to study lactone ring formation by the oxidative cyclization of catechol 30 and veratrole 38 have been thwarted by an inability to prepare the former substrate and decomposition of the latter. The reported conversions 44 → 45 and 46 → 47 suggest that a C2-carboxy group attached to the pyrrole ring can ‘direct’ the oxidative cyclization of N-tethered aryl groups. The acquisition of compound 22 by the means described herein provides an adventitious and concise route to the racemic modification of the pyrrolo[2,1-a]isoquinoline alkaloid crispine A (52).

Undecagold labeling of tRNA

1991 ◽  
Vol 49 ◽  
pp. 44-45
Author(s):  
James F. Hainfeld ◽  
Kyra M. Alford ◽  
Mathias Sprinzl ◽  
Valsan Mandiyan ◽  
Santa J. Tumminia ◽  
...  
Keyword(s):  
High Resolution ◽  
Transmission Electron Micrograph ◽  
Anticodon Loop ◽  
Electron Micrograph ◽  
Reaction Conditions ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

Dimensionally-Controlled Hydrothermal Tm3+-doped Oxidic Nanocrystals and Their Photoluminescence Properties

2010 ◽  
Vol 1247 ◽  
Author(s):  
Rocío Calderón-Villajos ◽  
Carlos Zaldo ◽  
Concepción Cascales
Keyword(s):  
Single Crystals ◽  
Fluorescence Lifetimes ◽  
Photoluminescence Properties ◽  
Reaction Conditions ◽  
Hydrothermal Processes ◽  
Bulk Single Crystals ◽  
Template Free ◽  
Reaction Media

AbstractControlled reaction conditions in simple, template-free hydrothermal processes yield Tm-Lu2O3 and Tm-GdVO4 nanocrystals with well-defined specific morphologies and sizes. In both oxide families, nanocrystals prepared at pH 7 reaction media exhibit photoluminescence in ∼1.95 μm similar to bulk single crystals. For the lowest Tm3+ concentration (0.2 % mol) in GdVO4 measured 3H4 and 3F4 fluorescence lifetimes τ are very near to τrad.

Urea-Catalyzed Functionalization of Unactivated C–H Bonds

2020 ◽  
Author(s):  
Alex L. Bagdasarian ◽  
Stasik Popov ◽  
Benjamin Wigman ◽  
Wenjing Wei ◽  
woojin lee ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Organic Synthesis ◽  
High Energy ◽  
Acid Catalysts ◽  
Potential Utility ◽  
New Paradigm ◽  
Lewis Acid Catalysts ◽  
Reaction Conditions ◽  
Highly Active ◽  
Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

Urea-Catalyzed Functionalization of Unactivated C–H Bonds

2020 ◽  
Author(s):  
Alex L. Bagdasarian ◽  
Stasik Popov ◽  
Benjamin Wigman ◽  
Wenjing Wei ◽  
woojin lee ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Organic Synthesis ◽  
High Energy ◽  
Acid Catalysts ◽  
Potential Utility ◽  
New Paradigm ◽  
Lewis Acid Catalysts ◽  
Reaction Conditions ◽  
Highly Active ◽  
Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

Direct Cyclization of Alkenyl Thioester via Transition Metal‐hydrogen Atom Transfer/radical‐polar Crossover Mechanism

2019 ◽  
Author(s):  
Shiori Date ◽  
Kensei Hamasaki ◽  
Karen Sunagawa ◽  
Hiroki Koyama ◽  
Chikayoshi Sebe ◽  
...  
Keyword(s):  
Natural Products ◽  
Hydrogen Atom ◽  
Transition Metal ◽  
Hydrogen Atom Transfer ◽  
Synthetic Method ◽  
Atom Transfer ◽  
Reaction Conditions ◽  
Hydride Hydrogen ◽  
Sulfur Heterocycles ◽  
One Step

<div>We report here a catalytic, Markovnikov selective, and scalable synthetic method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, in one step from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. The powerful Co catalysis via a cobalt hydride hydrogen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by the extensive optimization of the reaction conditions and tuning of the thioester unit.</div>

Iterative Supervised Principal Component Analysis-Driven Ligand Design for Regioselective Ti-Catalyzed Pyrrole Synthesis

2020 ◽  
Author(s):  
Xin Yi See ◽  
Benjamin Reiner ◽  
Xuelan Wen ◽  
T. Alexander Wheeler ◽  
Channing Klein ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
De Novo ◽  
Principal Component ◽  
Component Analysis ◽  
Catalyst Design ◽  
Data Driven ◽  
Initial Reaction ◽  
Training Set ◽  
Reaction Conditions ◽  
Component Loadings

<div> <div> <div> <p>Herein, we describe the use of iterative supervised principal component analysis (ISPCA) in de novo catalyst design. The regioselective synthesis of 2,5-dimethyl-1,3,4-triphenyl-1H- pyrrole (C) via Ti- catalyzed formal [2+2+1] cycloaddition of phenyl propyne and azobenzene was targeted as a proof of principle. The initial reaction conditions led to an unselective mixture of all possible pyrrole regioisomers. ISPCA was conducted on a training set of catalysts, and their performance was regressed against the scores from the top three principal components. Component loadings from this PCA space along with k-means clustering were used to inform the design of new test catalysts. The selectivity of a prospective test set was predicted in silico using the ISPCA model, and only optimal candidates were synthesized and tested experimentally. This data-driven predictive-modeling workflow was iterated, and after only three generations the catalytic selectivity was improved from 0.5 (statistical mixture of products) to over 11 (> 90% C) by incorporating 2,6-dimethyl- 4-(pyrrolidin-1-yl)pyridine as a ligand. The successful development of a highly selective catalyst without resorting to long, stochastic screening processes demonstrates the inherent power of ISPCA in de novo catalyst design and should motivate the general use of ISPCA in reaction development. </p> </div> </div> </div>

Suzuki–Miyaura cross-coupling for chemoproteomic applications

2020 ◽  
Author(s):  
Jian Cao ◽  
Ernest Armenta ◽  
Lisa Boatner ◽  
Heta Desai ◽  
Neil Chan ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Cross Coupling ◽  
Protein Profiling ◽  
Protein Labeling ◽  
Caspase 8 ◽  
Complex Cell ◽  
Bioorthogonal Chemistry ◽  
Reaction Conditions ◽  
Target Deconvolution ◽  
Palladium Catalyzed

Bioorthogonal chemistry is a mainstay of chemoproteomic sample preparation workflows. While numerous transformations are now available, chemoproteomic studies still rely overwhelmingly on copper-catalyzed azide –alkyne cycloaddition (CuAAC) or 'click' chemistry. Here we demonstrate that gel-based activity-based protein profiling (ABPP) and mass-spectrometry-based chemoproteomic profiling can be conducted using Suzuki–Miyaura cross-coupling. We identify reaction conditions that proceed in complex cell lysates and find that Suzuki –Miyaura cross-coupling and CuAAC yield comparable chemoproteomic coverage. Importantly, Suzuki–Miyaura is also compatible with chemoproteomic target deconvolution, as demonstrated using structurally matched probes tailored to react with the cysteine protease caspase-8. Uniquely enabled by the observed orthogonality of palladium-catalyzed cross-coupling and CuAAC, we combine both reactions to achieve dual protein labeling.

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