Presence Of Cesium Carbonate Research Articles

Alkylation of 6-Polyfluoroalkyl-2-thiouracils with Haloalkanes

The structure of 6-polyfluoroalkyl-2-thiouracils and reactivity of nucleophilic centers in their molecules were analyzed by quantum chemical calculations. According to the experimental data, methylation of 6-polyfluoroalkyl-2-thiouracils with methyl iodide initially gives 2-methylsulfanyl-substituted pyrimidin-4-one and then S,N3- and S,O-dimethyl derivatives. The optimal conditions for the selective formation of the S, N3- isomer were heating in tert-butyl alcohol in the presence of cesium carbonate as a base. Ethylation of 6-polyfluoroalkyl-2-thiouracils afforded approximately equal amounts of S,N3- and S,O-dimethyl derivatives. S,N3-Dimethyl-substituted pyrimidines in boiling ethanol in the presence of potassium carbonate were converted into uracil potassium salts as a result of nucleophilic substitution of the methylsulfanyl group by ethoxy and subsequent dealkylation of the latter.

Design and Synthesis of Novel Functionalized Fused Oxazepine and Diazepine Analogues Containing Coumarin Backbone through Domino Reaction

AbstractA simple and straightforward approach has been developed for the synthesis of functionalized fused oxazepine and diazepine analogues containing coumarin backbone. The approach was done through three‐component reaction of 4‐chloro‐3‐formylcoumarin, triphenyl‐λ5‐phosphanylidene derivatives and 2‐aminophenol or o‐phenylenediamine derivatives in the presence of cesium carbonate at room temperature. Carrying out the same reaction without base led to 4‐aminoarylcoumarins. Mild reaction conditions and synthesis of fused functionalized heterocyclic backbones are advantages of this approach.

Cu-catalyzed arylation of 1-acyl-1H-1,2,3-Benzotriazoles via C–N activation

An efficient copper-catalyzed arylation reaction of 1-acyl-1H-1,2,3-benzotriazoles with diaryliodonium salts via C–N activation is explored. The reaction is conducted regioselectively to form 1-aryl-1H-1,2,3-benzotriazoles in MeCN at 80 °C in the presence of cesium carbonate. 29 examples are given with the product yield of up to 84%. The probable reaction mechanism is proposed.

Copper Immobilized on Isonicotinic Acid Hydrazide Functionalized Nano‐Magnetite as a Novel Recyclable Catalyst for Direct Synthesis of Phenols and Anilines

AbstractA new nano‐catalyst which contains a core of magnetic Fe3O4 nanoparticles (NPs) has been fabricated. It is covered via isonicotinic acid hydrazide and copper (Cu). In this sense, Isonicotinic acid hydrazide (INH) is applied because of its ability as a bidendental ligand and pharmaceutical activity in order to be used for the complexion and connection of Cu on Fe3O4 surface for the synthesis of Fe3O4@INH@Cu (INH= Isonicotinic acid hydrazide). In this regard, Fe3O4@INH@Cu as a heterogeneous nanocatalyst for the cross‐coupling of aryl halides with potassium hydroxide (KOH) as the hydroxide source and ammonium acetate (NH4OAc), as the amine source in the presence of cesium carbonate (Cs2CO3) in polyethylene glycol (PEG‐400), has been applied. The catalyst is a new magnetically recyclable catalytic system with easy preparation and purification, high activity, eco‐friendly and economic advantages.

Cs2CO3‐Mediated Vicinal Thiosulfonylation of 1,1‐Dibromo‐1‐Alkenes with Thiosulfonates: An Expedient Synthesis of (E)‐1,2‐Thiosulfonylethenes

AbstractA new and highly efficient vicinal thiosulfonylation of 1,1‐dibromo‐1‐alkenes with thiosulfonates in the presence of cesium carbonate has been developed. The metal‐free diheterofunctionalization is an operationally simple to access a wide range of (E)‐1,2‐thiosulfonylethenes (α‐aryl‐β‐thioarylvinyl sulfones) in moderate to high yields with high levels of stereoselectivities. Further, scalable reactions have been demonstrated for this transformation, thus illustrating its efficiency and practicality.magnified image

Cesium Carbonate-Promoted P-Alkylation of Phosphinecarboxamides

An effective method for the P-alkylation of N-arylphosphinecarboxamides was demonstrated. Primary N-arylphosphinecarboxamides without additional protection underwent P-monoalkylation with various alkyl halides in the presence of cesium carbonate as a promoter. The reactivity of phosphinecarboxamides was also explored.

A Domino Approach for the Synthesis of α,β‐Epoxy Ketones from Carbonyl Compounds under Neat Conditions at Ambient Temperature

AbstractAn efficient method has been developed for the synthesis of α,β‐epoxy ketones from one pot reaction between aldehydes and ketones in presence of cesium carbonate and tert‐butyl hydrogen peroxide (TBHP) under neat conditions. In this methodology we have used the one pot domino type reaction with aldehydes and ketones to get α,β‐epoxy ketones without presynthesized chalcone precursors. A library of α,β‐epoxy ketones having a variety of substituents has been synthesized. Clean reaction, mild reaction conditions, ease of product isolation/purification, easily accessible reactants, wide substrates scope and metal and solvent‐free and environmental friendly reaction conditions are the notable advantages of the present method. The present methodology is applicable to gram scale synthesis.

Copper-Catalyzed Alkenylation of Cyanamides.

An efficient procedure for the copper-catalyzed cross-coupling between a broad range of cyanamides and iodoalkenes is reported. Upon reaction with catalytic amounts of copper(I) iodide and 2,2'-bisimidazole in the presence of cesium carbonate in DMF at 80 °C, a fast, regioselective, and stereoretentive cross-coupling occurs. This reaction, which was found to have a broad substrate scope, provides the first general entry to N-alkenylcyanamides, building blocks that hold great synthetic potential.

Regioselective Mono‐aza‐Michael Additions of Divinyl Ketones with Benzotriazole and Other N‐Heterocycles

The mono‐aza‐Michael additions of divinyl ketones with benzotriazole and other N‐heterocycles in the presence of cesium carbonate were described. This protocol has advantages of high regioselectivity, high yield, and mild condition.

Copper(0) Nanoparticles Supported on Al2O3 as Catalyst for Carboxylation of Terminal Alkynes

The copper particles, supported on Al2O3 were for the first time used as heterogeneous, highly active, easily available, and recyclable copper catalyst of direct carboxylation of various terminal alkynes with CO2 (2 bar) in the presence of cesium carbonate, allowing for the synthesis of alkyl 2-alkynoates. The catalyst contains large-scale CuNPs covered by oxide layer and less prone to erosion, resulting in its high selectivity and efficiency unusual for the particles of this size.

Catalytic thiomethylation of N-substituted ureas and thioureas with N,N,N′,N′-tetramethylmethanediamine and α,ω-alkanedithiols

An efficient procedure has been developed for the synthesis of N,N′-(2,5-dithiaalkane-α,ω-diyl)bis-(N′-allylthioureas) by thiomethylation of N-substituted ureas and thioureas with α,ω-alkanedithiols and N,N,N′,N′-tetramethylmethanediamine in the presence of cesium carbonate as catalyst.

Pd‐Catalyzed C−H Arylation of Benzothiazoles with Diaryliodonium Salt: One‐Pot Synthesis of 2‐Arylbenzothiazoles

AbstractA simple and direct arylation of benzothiazoles in the presence of diaryliodonium salts to afford 2‐arylbenzothiazoles has been developed. This cross‐coupling reaction is catalyzed by palladium bromide in the presence of cesium carbonate and a phosphorus ligand. The protocol has a broad substrate scope and is tolerant towards a wide range of functional groups to give the desired products in moderate to high yields.

Selective S-methylation of highly fluorinated thiocarbamates

ABSTRACTA series of new S-methyl O-fluoroalkyl N-alkyl(aryl)imidothiocarbonates were prepared by S-methylation of various fluoroalkylated thiocarbamates with methyl iodide in the presence of cesium carbonate and tetrabutylammonium iodide (TBAI) in tetrahydrofuran (THF) at room temperature. As expected from the mostly soft electrophilic alkyl halide (MeI), no isomer products derived from N-methylation were detected. The products were characterized by spectroscopic (1H, 13C and 19F) NMR, infrared, and high-resolution mass spectrometric techniques.

ChemInform Abstract: Formal [4 + 1] Annulation of α‐Arylhydrazonoketones and Dimethylsulfoxonium Methylide: One‐Pot Synthesis of Substituted Pyrazoles and Dihydropyrazoles.

A formal [4 + 1] annulation of readily available α-arylhydrazonoketones and trimethylsulfoxonium iodide in the presence of cesium carbonate is described involving a sequential Corey–Chaykovsky reaction and intramolecular nucleophilic cyclization process. Substituted pyrazoles were obtained exclusively from the reactions of α-arylhydrazono-β-oxo-amides and trimethylsulfoxonium iodide in moderate to good yields, whereas the reactions of α-arylhydrazono-β-oxo-ketone/α-arylhydrazono- β-oxo-ester afforded the corresponding dihydropyrazoles in good yields.

Formal [4 + 1] Annulation of α-Arylhydrazonoketones and Dimethylsulfoxonium Methylide: One-pot Synthesis of Substituted Pyrazoles and Dihydropyrazoles.

A formal [4 + 1] annulation of readily available α-arylhydrazonoketones and trimethylsulfoxonium iodide in the presence of cesium carbonate is described involving a sequential Corey-Chaykovsky reaction and intramolecular nucleophilic cyclization process. Substituted pyrazoles were obtained exclusively from the reactions of α-arylhydrazono-β-oxo-amides and trimethylsulfoxonium iodide in moderate to good yields, whereas the reactions of α-arylhydrazono-β-oxo-ketone/α-arylhydrazono- β-oxo-ester afforded the corresponding dihydropyrazoles in good yields.

Palladium‐Catalyzed Two‐Component Domino Coupling Reaction of (Z)‐β‐Bromostyrenes with Norbornenes: Synthesis of 1,5‐Enynes

AbstractPolyfunctional molecules, 1,5‐enynes, have been achieved via a palladium(0)‐catalyzed domino coupling reaction of (Z)‐β‐bromostyrenes with norbornenes in the presence of cesium carbonate and N,N‐dimethylformamide. The process involves a double Heck‐type procedure, two‐fold C(sp2)H activation and formation of two carbon‐carbon bonds. There are possibilities of diversified transformation for the domino coupling of (Z)‐β‐bromostyrenes with norbornenes, the procedure is successfully driven to 1,5‐enynes via accurate adjustment of the reaction conditions.magnified image

Nucleophilic arylation with tetraarylphosphonium salts

Organic phosphonium salts have served as important intermediates in synthetic chemistry. But the use of a substituent on the positive phosphorus as a nucleophile to construct C–C bond remains a significant challenge. Here we report an efficient transition-metal-free protocol for the direct nucleophilic arylation of carbonyls and imines with tetraarylphosphonium salts in the presence of caesium carbonate. The aryl nucleophile generated from phosphonium salt shows low basicity and good nucleophilicity, as evidenced by the successful conversion of enolizable aldehydes and ketones. The reaction is not particularly sensitive to water, shows wide substrate scope, and is compatible with a variety of functional groups including cyano and ester groups. Compared with the arylmetallic reagents that are usually moisture sensitive, the phosphonium salts are shelf-stable and can be easily handled.

Benign Perfluoroalkylation of Aniline Derivatives through Photoredox Organocatalysis under Visible‐Light Irradiation

AbstractIn this work, we present a room‐ or solar‐light‐initiated transition‐metal‐free radical homolytic aromatic substitution (HAS) reaction of aniline derivatives with perfluoroalkyl moieties employing perfluoroalkyl halides as readily available perfluoroalkyl sources in the presence of cesium carbonate as base and inexpensive Rose Bengal as organophotocatalyst in MeCN as solvent, rendering perfluoroalkyl‐substituted aniline derivatives in good‐to‐excellent yields, even upon scaling up. Although the mechanism of this reaction is still under investigation, we shall present some evidence based on competitive substitution rate experiments that cast some light onto the reaction intermediates.

ChemInform Abstract: Synthesis of N2‐Arylaminopyrimidine‐5‐carbonitrile Derivatives via SNAr Amination Reaction.

Abstractscope and limitations of the new protocol

ChemInform Abstract: Investigations of Scope and Mechanism of Nickel‐Catalyzed Transformations of Glycosyl Trichloroacetimidates to Glycosyl Trichloroacetamides and Subsequent, Atom‐Economical, One‐Step Conversion to α‐Urea‐Glycosides.

The development and mechanistic investigation of a highly stereoselective methodology for preparing α-linked-urea neo-glycoconjugates and pseudo-oligosaccharides is described. This two-step procedure begins with the selective nickel-catalyzed conversion of glycosyl trichloroacetimidates to the corresponding α-trichloroacetamides. The α-selective nature of the conversion is controlled with a cationic nickel(II) catalyst, [Ni(dppe)(OTf)2 ] (dppe=1,2-bis(diphenylphosphino)ethane, OTf=triflate). Mechanistic studies have identified the coordination of the nickel catalyst with the equatorial C2 -ether functionality of the α-glycosyl trichloroacetimidate to be paramount for achieving an α-stereoselective transformation. A cross-over experiment has indicated that the reaction does not proceed in an exclusively intramolecular fashion. The second step in this sequence is the direct conversion of α-glycosyl trichloroacetamide products into the corresponding α-urea glycosides by reacting them with a wide variety of amine nucleophiles in presence of cesium carbonate. Only α-urea-product formation is observed, as the reaction proceeds with complete retention of stereochemical integrity at the anomeric CN bond.