scholarly journals Sulphide as a leaving group: highly stereoselective bromination of alkyl phenyl sulphides

2019 ◽  
Vol 10 (39) ◽  
pp. 9042-9050 ◽  
Author(s):  
Daniele Canestrari ◽  
Caterina Cioffi ◽  
Ilaria Biancofiore ◽  
Stefano Lancianesi ◽  
Lorenza Ghisu ◽  
...  
Keyword(s):  
Molecular Bromine ◽  
Reaction Conditions ◽  
Leaving Group

Molecular bromine is shown to stereoselectively brominate readily available alkyl phenyl sulphides under exceptionally mild reaction conditions.

Isoquinoline-1-Carboxylate as a Traceless Leaving Group for Chelation-Assisted Glycosylation under Mild and Neutral Reaction Conditions

2017 ◽  
Vol 56 (49) ◽  
pp. 15698-15702 ◽  
Author(s):  
Hao-Yuan Wang ◽  
Christopher J. Simmons ◽  
Stephanie A. Blaszczyk ◽  
Paul G. Balzer ◽  
Renshi Luo ◽  
...  
Keyword(s):  
Reaction Conditions ◽  
Neutral Reaction ◽  
Leaving Group

scholarly journals Die unterschiedliche Reaktivität von 1,4-Disilabutan und n-Tetrasilan gegenüber sekundären Aminen / Differences in Reactivity of 1,4-Disilabutane and n-Tetrasilane towards Secondary Amines

1990 ◽  
Vol 45 (12) ◽  
pp. 1679-1683 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Heinz Schuh
Keyword(s):  
Silicon Nitride ◽  
Model Systems ◽  
Secondary Amines ◽  
Cleavage Reaction ◽  
Reaction Conditions ◽  
Two Phase ◽  
Leaving Group

1,4-Disilabutane H3SiCH2CH2SiH3 (1) and n-tetrasilane H3SiSiH,SiH2SiH3 were employed as model systems for the preparation of silicon-rich aminosilanes potentially useful for the deposition of silicon nitride Si3N4. 1 reacts with the appropriate equivalents of diethylamine in an alkane solvent and in the presence of the two-phase catalyst NaNH2/18-crown-6 to give the products (Et,N)2SiHCH2CH2SiH3, (Et2N)2SiHCH2CH2SiH2(NEt2), and (Et2N)2SiHCH2CH2SiH(NEt2)2. By contrast, n-Si4H10 undergoes a cleavage reaction under similar conditions to yield H3SiNEt2 and H2Si(NEt2)2 together with a mixture of polysilanes SinH2n+2, the composition of which is depending on the reaction conditions and the nature of the catalyst (NaH and NaNH2). Diethylaminopolysilanes are also formed, but only in trace quantities. Treatment of n-Si4H10 with pyrrole (C4H5N) leads to the formation of trisilane accompanied by the pyrrolylsilanes H2Si(C4H4N)2, HSi(C4H4N)3, and Si(C4H4N)4. The differences in reactivity suggest excellent leaving group properties of silyl anions in the reaction with amines.

scholarly journals The Cyclopropane Ring as a Reporter of Radical Leaving-Group Reactivity for Ni-Catalyzed C(sp3)–O Arylation

2020 ◽  
Author(s):  
Reginald Mills ◽  
John. J. Monteith ◽  
Sophie Rousseaux
Keyword(s):  
Cyclopropane Ring ◽  
Catalytic Cycle ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Design And Optimization ◽  
Redox Active ◽  
Leaving Group

<div><p>The ability to understand and predict reactivity is highly important for the development of new reactions. In the context of Ni-catalyzed C(sp<sup>3</sup>)–O functionalization, we have developed a unique strategy employing activated cyclopropanols to aid the design and optimization of a redox-active leaving group for C(sp<sup>3</sup>)–O arylation. In this chemistry, the cyclopropane ring acts as a reporter of leaving-group reactivity, since the ring-opened product is obtained under polar (2e) conditions, and the ring-closed product is obtained under radical (1e) conditions. Mechanistic studies demonstrate that the optimal leaving group is redox-active, and are consistent with a Ni(I)/Ni(III) catalytic cycle. The optimized reaction conditions are also used to synthesize a number of arylcyclopropanes, which are valuable pharmaceutical motifs.</p></div>

scholarly journals How Do Aromatic Nitro Compounds React with Nucleophiles? Theoretical Description Using Aromaticity, Nucleophilicity and Electrophilicity Indices

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4819
Author(s):  
Kacper Błaziak ◽  
Witold Danikiewicz ◽  
Mieczysław Mąkosza
Keyword(s):  
Kinetic Isotope Effect ◽  
Theoretical Description ◽  
Reaction Conditions ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Leaving Group ◽  
Aromatic Nitro ◽  
Rate Limiting ◽  
Reaction Direction

In this study, we present a complete description of the addition of a model nucleophile to the nitroaromatic ring in positions occupied either by hydrogen (the first step of the SNAr-H reaction) or a leaving group (SNAr-X reaction) using theoretical parameters including aromaticity (HOMA), electrophilicity and nucleophilicity indices. It was shown both experimentally and by our calculations, including kinetic isotope effect modeling, that the addition of a nucleophile to the electron-deficient aromatic ring is the rate limiting step of both SNAr-X and SNAr-H reactions when the fast transformation of σH-adduct into the products is possible due to the specific reaction conditions, so this is the most important step of the entire reaction. The results described in this paper are helpful for better understanding of the subtle factors controlling the reaction direction and rate.

scholarly journals The Cyclopropane Ring as a Reporter of Radical Leaving-Group Reactivity for Ni-Catalyzed C(sp3)–O Arylation

2020 ◽  
Author(s):  
Reginald Mills ◽  
John. J. Monteith ◽  
Sophie Rousseaux
Keyword(s):  
Cyclopropane Ring ◽  
Catalytic Cycle ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Design And Optimization ◽  
Redox Active ◽  
Leaving Group

<div><p>The ability to understand and predict reactivity is highly important for the development of new reactions. In the context of Ni-catalyzed C(sp<sup>3</sup>)–O functionalization, we have developed a unique strategy employing activated cyclopropanols to aid the design and optimization of a redox-active leaving group for C(sp<sup>3</sup>)–O arylation. In this chemistry, the cyclopropane ring acts as a reporter of leaving-group reactivity, since the ring-opened product is obtained under polar (2e) conditions, and the ring-closed product is obtained under radical (1e) conditions. Mechanistic studies demonstrate that the optimal leaving group is redox-active, and are consistent with a Ni(I)/Ni(III) catalytic cycle. The optimized reaction conditions are also used to synthesize a number of arylcyclopropanes, which are valuable pharmaceutical motifs.</p></div>

scholarly journals 5-Membered cyclic ethers via phenonium ion mediated cyclization through carbonate chemistry

2018 ◽  
Vol 90 (1) ◽  
pp. 93-107 ◽  
Author(s):  
Fabio Aricò ◽  
Andrea Maranzana ◽  
Manuele Musolino ◽  
Pietro Tundo
Keyword(s):  
Intramolecular Cyclization ◽  
Theoretical Calculations ◽  
Cyclic Ether ◽  
Hydroxyl Group ◽  
Cyclic Ethers ◽  
Carbonate Chemistry ◽  
Reaction Conditions ◽  
Leaving Group ◽  
Acidic Conditions ◽  
First Time

AbstractCyclization of 2-(2-hydroxyethyl)phenol via DMC chemistry in acidic conditions is herein discussed for the first time. Reaction conditions have been investigated and optimized. This substrate is quite appealing as it incorporates a 2-hydroxyethyl moiety in ortho to the aromatic hydroxyl group capable of stabilizing the related phenonium ion. When the reaction mechanism was investigated via theoretical calculations, the results suggest that the most favorable pathway encompasses a DMC-mediated formation of the phenonium ion that is converted into the 2-(2-methoxyethyl)phenol. The related cyclic ether is then formed via intramolecular cyclization of this intermediate. This peculiar cyclization reaction is another example of the versatility of DMC herein used as solvent, methoxycarbonylation agent and leaving group in the intramolecular cyclization leading to the phenonium ion.

Isoquinoline-1-Carboxylate as a Traceless Leaving Group for Chelation-Assisted Glycosylation under Mild and Neutral Reaction Conditions

2017 ◽  
Vol 129 (49) ◽  
pp. 15904-15908 ◽  
Author(s):  
Hao-Yuan Wang ◽  
Christopher J. Simmons ◽  
Stephanie A. Blaszczyk ◽  
Paul G. Balzer ◽  
Renshi Luo ◽  
...  
Keyword(s):  
Reaction Conditions ◽  
Neutral Reaction ◽  
Leaving Group

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>

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