scholarly journals Palladium-catalyzed α-arylation for the addition of small rings to aromatic compounds

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Zhi-Tao He ◽  
John F. Hartwig
Keyword(s):  
Electronic Properties ◽  
Aromatic Compounds ◽  
Ring Opening ◽  
Biologically Active ◽  
High Yield ◽  
Protecting Group ◽  
Mechanistic Studies ◽  
Claisen Condensation ◽  
Wide Range ◽  
Palladium Catalyzed

Abstract Small, strained rings have rigid, defined conformations and unique electronic properties. For these reasons, many groups seek to use these subunits to form biologically active molecules. We report a generally applicable approach to attach small rings to a wide range of aromatic compounds by palladium-catalyzed α-arylation of cyclopropyl, cyclobutyl and azetidinyl esters. The direct α-arylation of cyclopropyl esters and cyclobutyl esters is achieved in high yield by ensuring that the rate of coupling exceeds the rate of Claisen condensation. The α-arylation of azetidines is achieved without ring opening of the strained saturated heterocycle by conducting the reactions with an azetidine derivative bearing a benzyl protecting group on nitrogen. Mechanistic studies show that the α-arylation of small rings is challenging because of the weak acidity of α C-H bond (cyclopropanes), strong sensitivity of the strained esters to Claisen condensation (cyclobutatanes), or facile decomposition of the enolates (azetidinyl esters).

scholarly journals SnCl4-catalyzed Solvent-free Acetolysis of 2,7-Anhydrosialic Acid Derivatives

2019 ◽  
Author(s):  
Kesatebrhan Haile Asressu ◽  
Cheng-Chung Wang
Keyword(s):  
Sialic Acid ◽  
Lewis Acids ◽  
Ring Opening ◽  
Building Blocks ◽  
Solvent Free ◽  
Biologically Active ◽  
Protecting Group ◽  
Free Ring ◽  
Ring Opening Reactions ◽  
Acid Catalyzed

Sialic acid-containing glycans are found in different sialic acid forms and a variety of glycosidic linkages in biologically active glycoconjugates. Hence, the preparation of suitably protected sialyl building blocks requires high attention in order to access glycans in pure form. In this line, various C-5 substituted 2,7-anhydrosialic acid derivatives bearing both electron donating and withdrawing protecting groups were synthesized and subjected to different Lewis acid-catalyzed solvent free ring opening reactions at room temperature in the presence of acetic anhydride. Among the various Lewis acids tested, the desired acetolysized products were obtained in moderate yields under a tin(IV) chloride catalysis system. Our methodology can be extended to regioselective protecting group installation and manipulation towards a number of thiosialoside and halide donors.

scholarly journals Palladium-Catalyzed Cross-Coupling of Gem-Bromofluoroalkenes with Alkylboronic Acids for the Synthesis of Alkylated Monofluoroalkenes

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5532
Author(s):  
Laëtitia Chausset-Boissarie ◽  
Nicolas Cheval ◽  
Christian Rolando
Keyword(s):  
Organic Synthesis ◽  
Functional Group ◽  
Materials Science ◽  
Cross Coupling ◽  
High Yield ◽  
Efficient Synthesis ◽  
Mild Conditions ◽  
Wide Range ◽  
Palladium Catalyzed ◽  
Novel Strategy

Monofluoroalkenes are versatile fluorinated synthons in organic synthesis, medicinal chemistry and materials science. In light of the importance of alkyl-substituted monofluoroalkenes efficient synthesis of these moieties still represents a synthetic challenge. Herein, we described a mild and efficient methodology to obtain monofluoroalkenes through a stereospecific palladium-catalyzed alkylation of gem-bromofluoroalkenes with primary and strained secondary alkylboronic acids under mild conditions. This novel strategy gives access to a wide range of functionalized tri- and tetrasubstituted monofluoroalkenes in high yield, with good functional group tolerance, independently from the gem-bromofluoroalkenes geometry.

scholarly journals Electrochemical Synthesis of Allylic Amines from Alkenes and Amines

2021 ◽  
Author(s):  
Diana Wang ◽  
Karina Targos ◽  
Zachary Wickens
Keyword(s):  
Aliphatic Amine ◽  
Reactive Intermediates ◽  
Building Blocks ◽  
Electrochemical Process ◽  
Biologically Active ◽  
Secondary Amines ◽  
High Yield ◽  
Mechanistic Studies ◽  
Allylic Amines ◽  
Synthetic Strategy

Allylic amines are valuable synthetic targets en route to diverse biologically active amine products. Current allylic C–H amination strate-gies remain limited with respect to the viable N-substituents. Herein we disclose a new electrochemical process to prepare aliphatic allylic amines by coupling two abundant starting materials: secondary amines and unactivated alkenes. This oxidative transformation proceeds via electrochemical generation of an electrophilic adduct between thianthrene and the alkene substrates. Treatment of these adducts with aliphatic amine nucleophiles and base provides allylic amine products in high yield. This synthetic strategy is also amenable to functionali-zation of feedstock gaseous alkenes at 1 atmosphere. In the case of 1-butene, remarkable Z-selective crotylation is observed. This strategy, however, is not limited to the synthesis of simple building blocks; complex biologically active molecules are suitable as both alkene and amine coupling partners. Preliminary mechanistic studies implicate vinylthianthrenium salts as key reactive intermediates.

Palladium-Catalyzed Ring-Opening Coupling of Cyclobutenols with Aryl Halides

Synlett ◽  
2017 ◽  
Vol 29 (06) ◽  
pp. 754-758 ◽  
Author(s):  
Takanori Matsuda ◽  
Takeshi Matsumoto ◽  
Akira Murakami
Keyword(s):  
Aromatic Compounds ◽  
Ring Opening ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Aryl Halides ◽  
Ortho Position ◽  
Unsaturated Ketones ◽  
Cross Coupling Reaction ◽  
Palladium Catalyzed ◽  
Intramolecular Condensation

A palladium(0)-catalyzed ring-opening cross-coupling reaction between tert-cyclobutenols and aryl halides produces γ-arylated β,γ-unsaturated ketones. In the case of aryl halides bearing functional groups at the ortho position, the resulting ring-opened ketones undergo intramolecular condensation to afford bicyclic aromatic compounds.

scholarly journals CuH-Catalyzed Enantioselective Ketone Allylation with 1,3-Dienes: Scope, Mechanism, and Applications

2018 ◽  
Author(s):  
Chengxi Li ◽  
Richard Liu ◽  
Luke T. Jesikiewicz ◽  
Yang Yang ◽  
Peng Liu ◽  
...  
Keyword(s):  
Density Functional ◽  
Building Blocks ◽  
Biologically Active ◽  
High Yield ◽  
Organometallic Reagents ◽  
Carbon Nucleophiles ◽  
Homoallylic Alcohols ◽  
Alcohol Synthesis ◽  
Wide Range ◽  
Pharmaceutical Agents

<p>Chiral tertiary alcohols are important building blocks for the synthesis of pharmaceutical agents and biologically active natural products. The addition of carbon nucleophiles to ketones is the most common approach to tertiary alcohol synthesis, but traditionally relies on stoichiometric organometallic reagents that are difficult to prepare, sensitive, and uneconomical. We describe a mild and efficient method for the copper-catalyzed allylation of ketones, using widely available 1,3-dienes as allylmetal surrogates. Homoallylic alcohols bearing a wide range of functional groups are obtained in high yield and with good regio-, diastereo-, and enantioselectivity. Mechanistic investigations using density functional theory (DFT) implicate the in situ formation of a rapidly equilibrating mixture of isomeric copper(I) allyl complexes, from which Curtin-Hammett kinetics determine the major isomer of product. A stereochemical model is provided to explain the high diastereo- and enantioselectivity of this process. Finally, this method was applied toward the preparation of an important drug, (R)-Procyclidine, and a key intermediate in the synthesis of several pharmaceuticals.</p> <br>

scholarly journals ALGORITHM OF RECEIVING HIGH YIELD OF POTATOES

2018 ◽  
Vol 13 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Фания Замалиева ◽  
Faniya Zamalieva ◽  
Гульгуна Сафиуллина ◽  
Gul'guna Safiullina ◽  
Татьяна Жарёхина ◽  
...  
Keyword(s):  
Seed Quality ◽  
Biologically Active ◽  
High Yield ◽  
Quality Factors ◽  
Experimental Conditions ◽  
Seed Material ◽  
Wide Range ◽  
Potato Yields ◽  
Healthy Seed

The potato yield, planned on the basis of calculated methods of fertilizer application, in practice can fluctuate over a wide range. Many factors influence the increase in the removal of nutrients and potato yields. One of the most important factors for potatoes, as a vegetatively propagated culture, is the quality of the seed material. The purpose of the research was to substantiate the algorithm for obtaining high potato yields on the basis of determining the influence on the productivity of quality factors of seed material, the background of fertilizers, irrigation, the use of chemical etchant and biologically active preparations. Experiments of Kortni and Nevskiy varieties were conducted in Laishevsky district of the Republic of Tatarstan. It was revealed that in gray forest soils under experimental conditions, the optimal background of fertilizers with the main application on the bog was N120P140K140, on irrigation - N100P120K120. Higher doses of fertilizers on irrigation and on the bog caused lower yields. The use of the Maksim chemical preservative on the bog in the arid conditions of the year increased productivity by 6.0 ... 12.0%, on irrigation - reduced by 18.0 ... 24.6%. Biologically active preparations increased productivity in moist soil by 14.0 ... 17.0%. The consistent increase in the yield of a healthy seed of Kortni variety occurred under the influence of factors: the quality of seed material - from 10 to 15.5 tons per hectare - by 55%, the background of fertilizers N100P120K120- from 15.5 to 26.3 tons per hectare - by 70% irrigation - from 26.3 to 54.0 tons per hectare - by 105.3%, treatment with zircon - from 54.0 to 61.5 tons per hectare - by 14%. Against the backdrop nutrition of N100P120K120, calculated to yield of 20 tons per hectare, with additional factors, a yield of 61.5 tons per hectare (+ 208%) was obtained. In the degenerate seed material of Nevskiy variety, the increase in productivity with the progressive use of factors occurred to a much lesser extent: from the quality of the seed material - from 10.0 to 12.0 tons per hectare - by 20%, the fertilizer background N100P120K120 - from 12 to 17.5 tons per hectare - by 46%, irrigation - from 17.5 to 23 tons per hectare by 31.4%. Against the nutrition backdrop of N100P120K120, calculated to yield of 20 tons per hectare, Nevskiy yielded 23 tons per hectare (+ 15%). The importance of seed quality is a key in obtaining high yields of potatoes. In healthy seed potatoes, with additional factors - irrigation, fertilizers, BAP - much higher yields are created, compared to the addition of the degenerate seed material under the same conditions. On the basis of the obtained results, the following algorithm for applying the factors for obtaining high potato productivity is recommended: healthy seeds + irrigation + fertilizers + biologics.

scholarly journals SnCl4-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

2019 ◽  
Vol 15 ◽  
pp. 2990-2999
Author(s):  
Kesatebrhan Haile Asressu ◽  
Cheng-Chung Wang
Keyword(s):  
Sialic Acid ◽  
Lewis Acids ◽  
Ring Opening ◽  
Building Blocks ◽  
Solvent Free ◽  
Biologically Active ◽  
Protecting Group ◽  
Free Ring ◽  
Ring Opening Reactions ◽  
Acid Catalyzed

Sialic acid-containing glycans are found in different sialic acid forms and a variety of glycosidic linkages in biologically active glycoconjugates. Hence, the preparation of suitably protected sialyl building blocks requires high attention in order to access glycans in a pure form. In line with this, various C-5-substituted 2,7-anhydrosialic acid derivatives bearing both electron-donating and -withdrawing protecting groups were synthesized and subjected to different Lewis acid-catalyzed solvent-free ring-opening reactions at room temperature in the presence of acetic anhydride. Among the various Lewis acids tested, the desired acetolysis products were obtained in moderate yields under tin(IV) chloride catalysis. Our methodology could be extended to regioselective protecting group installations and manipulations towards a number of thiosialoside and halide donors.

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