Presence Of Potassium Tert-butoxide Research Articles

1,3-Dipolar Cycloaddition of Diazophosphonates with Methyl(Ethyl) Acrylate for the Synthesis of 5-Arylpyrazole-3-carboxylates

A wide range of -aryl--diazophosphonates was easily prepared via modified diazo transfer reaction. Benzylphoshonates reacted with tosyl azide (TsN3) in the presence of potassium tert-butoxide (KOtBu) to afford diazophosphonates in yields up to 93% (generally 70-80%). Aryl-diazophosponates were successfully explored for the synthesis of 5-aryl substituted pyrazol-3-carboxylates in one pot by the 1,3-dipolar cycloaddition with alkyl acrylates followed by NaH treatment. The second stage led to elimination of the diethoxylphosphoryl moiety with the aromatization of cycle.

Oxidative depolymerization of kraft lignin assisted by potassium tert-butoxide and its effect on color and UV absorption

A chemically mild methodology was demonstrated to obtain decomposed lignin products via oxidative depolymerization. We effectively produced light-colored lignin materials with low molecular weight and narrow molecular weight distribution by simple agitation at ambient temperature and pressure in the presence of potassium tert-butoxide and gaseous oxygen. This oxidative depolymerization dissociated various lignin bonding structures and oxidized aliphatic hydroxyl groups of lignin, expanding conjugated system within the depolymerized lignin molecules. This chemical transformation resulted in the generation of effective chromophoric moieties to enhance the UV absorption property of the resulting depolymerized products, which showed a significant improvement in the sun protection capability.

Nickel-Catalyzed Defluorophosphonylation of Aryl Fluorides.

A Ni-catalyzed cross-coupling reaction between aryl fluorides and dialkyl phosphonates [HP(O)(OR)2] (R = secondary alkyl groups) in the presence of potassium tert-butoxide as a base is reported. The reaction converted various aryl fluorides into the corresponding aryl phosphonates even when electron-donating substituents were present on the aromatic ring. The combined experimental and computational studies suggested Ni-K+ cooperative action of a Ni(0) complex chelated with a strongly electron-donating ion-bridged dimeric phosphite ligand system [P(OR)2O-K+]2 that facilitates turnover-limiting C-F bond oxidative addition of aryl fluorides.

Synthesis of α-Aryldiazophosphonates via a Diazo Transfer Reaction.

The simple synthetic procedure for preparation of α-aryl-α-diazophosphonates via a diazo transfer reaction is proposed. Benzylphosphonates reacted with tosyl azide (TsN3) in the presence of potassium tert-butoxide (KOtBu) to afford diazophosphonates in a yield up to 79%. The proposed method is general. The reaction uses easily available starting materials, tolerates various functional groups, and may be applied for multi-gram scale synthesis.

Synthesis of Pyrimidinyl Benzazolyl Urea Derivatives as Antimicrobial and Antioxidant Agents

A library of pyrimidinyl benzazolyl urea derivatives were synthesized from pyrimidine-2- amine and methyl benzazolylcarbamate in the presence of potassium tert-butoxide in DMF. The compounds with benzothiazolyl and benzimidazolyl moieties having chloro and nitro substituents on the aromatic ring exhibited prominent antibacterial activity against Bacillus subtilus. Nitro substituted pyrimidinyl benzothiazolyl urea and pyrimidinyl benzimidazolyl urea displayed prominent antifungal activity against Asperigellus niger. The compounds with benzoxazole moiety showed greater radical scavenging activity than those with benzothiazole and benzimidazole units.

KOtBu-BF3.OEt2 mediated synthesis of quinazolin-4(3H)-ones from 2-substituted amides with nitriles and aldehydes

KOtBu-BF3.OEt2 mediated synthesis of quinazolin-4(3H)-ones from 2-substituted amides with nitriles and aldehydes have been developed. In this protocol, a variety of nitriles as well as aldehydes react with 2-substituted benzamides to corresponding quinazolin-4(3H)-ones products in good to moderate yields, via the cleavage of C-X and C-N bonds and the formation of double C-N bonds simultaneously, in presence of potassium tert-butoxide.

Cationic living polymerization of cyclic dithiocarbonates involving sulfide-migration

Ring-opening polymerization of cyclic dithiocarbonates was attempted by varying reaction conditions (temperature, concentration, and solvents) to achieve a high polymer conversion. The participation of neighboring sulfide groups in the ring opening was demonstrated by selective sulfide migration and evaluated by composition analysis of the resulting copolymer. The migration was accelerated by electron-enriching substituents on the aryl sulfide and led to the formation of homopolymers with alkyl sulfides. The isomerization of the monomer encountered in the polymerization reduced with sulfide migration and exclusively occurred as substituted by a trityl sulfide. Three catalytic isomerization pathways were proposed for the polymerization mechanism, wherein the electronic and steric contributions of a substituted sulfide group were considered to rationalize the competitive formation of polymers and isomers. The polymerization of a monomer carrying two neighboring groups of butyl sulfide and benzoate proceeded to homopolymerization involving the migration of a sulfide group. The preferential migration was confirmed by the isolation of a six-membered cyclic carbonate as the main fragment product of depolymerization that occurred in the presence of potassium tert-butoxide. A reactive chain end in living polymerization was modified by an in situ reaction with sodium dithiocarbamate. A linear correlation between experimental and theoretical number average molecular weights of the prepared polymers was investigated with polymer conversion variance. The neutralized chain-end improved the chemical stability of the prepared poly(dithiocarbonate)s, and a stable polydispersity was obtained. The thermal decomposition temperature, Td (10% loss), of a polydithiocabonate was measured at 189 °C and the corresponding value after end-capping of the polymer was 285 °C.

T-BuOK-promoted methylthiolation of aryl fluorides with dimethyldisulfide under transition-metal-free and mild conditions

In the presence of potassium tert-butoxide (t-BuOK), the cross-coupling reaction between aryl fluorides and dimethyldisulfide was developed. A series of aryl methyl sulfides were obtained in moderate to good yields under transition-metal-free and mild conditions.

Organocatalyst in Direct C(sp2)-H Arylation of Unactivated Arenes: [1-(2-Hydroxyethyl)-piperazine]-Catalyzed Inter-/Intra-molecular C-H Bond Activation.

This article describes the identification of 1-(2-hydroxyethyl)-piperazine as a new, cost-effective, highly efficient organocatalyst, which promotes both inter- and intra-molecular direct C(sp2)-H arylations of unactivated arenes in the presence of potassium tert-butoxide. While the inter-molecular C-H arylation of unactivated benzenes with aryl halides (Ar-X; X = I, Br, Cl) toward biaryl syntheses underwent smoothly in the presence of only 10 mol % organocatalyst, the intra-molecular C-H arylation catalytic system composed of 40 mol % each of the catalyst and the additive (4-dimethylaminopyridine (DMAP)). The novel catalyst was also able to perform both inter- and intra-molecular direct arylations simultaneously in a single pot. The mechanistic studies confirmed the involvement of aryl radical anions and proceeded via a single-electron-transfer (SET) mechanism. The large substrate scope, high functional group tolerance, competition experiments, gram-scale synthesis, and kinetic studies further highlight the importance and versatile nature of the methodology as well as the compatibility of the new catalyst. To the best of our knowledge, this is the first report on any organocatalyst that reported detailed investigations of both inter- and intra-molecular direct C(sp2)-H arylations of unactivated arenes in a single representation.

Synthesis of aryl-substituted thieno[3,2-b]thiophene derivatives and their use for N,S-heterotetracene construction.

Fiesselmann thiophene synthesis was applied for the convenient construction of thieno[3,2-b]thiophene derivatives. Thus, new 5- or 6-aryl-3-hydroxythieno[3,2-b]thiophene-2-carboxylates were obtained by condensation of 5- or 4-aryl-3-chlorothiophene-2-carboxylates, respectively, with methyl thioglycolate in the presence of potassium tert-butoxide. The saponification of the resulting esters, with decarboxylation of the intermediating acids, gave the corresponding thieno[3,2-b]thiophen-3(2H)-ones. The latter ketones were used to synthesize new N,S-heterotetracenes, namely 9H-thieno[2',3':4,5]thieno[3,2-b]indoles by their treatment with arylhydrazines in accordance with the Fischer indolization reaction.

INVESTIGATION OF THE CATALYTIC EFFECT OF POTASSIUM TRET-BUTOXIDE IN THE AMIDATION REACTIONS OF RAPESEED OIL ACYLGLYCERIDES

Background. Alkalis and metal alkoxides are used as catalysts for the amidation of vegetable oils. However, the use of known catalysts does not always allow to soften the conditions of the processes to the required level. The use of potassium tret-butoxide as a catalyst for these reactions can serve as a solution to the problem.Objective. Verification of the use of potassium tert-butoxide as a catalyst for the amidation reaction of vegetable oil acylglycerides.Methods. To achieve this goal, a series of syntheses of the amidation of rapeseed oil with ethylenediamine, diethanolamine and dibutylamine in the presence of potassium tert-butylate was carried out. The dependences of the yields of the target product on the catalyst content, temperature and reaction time were studied.Results. It is shown that with the introduction of potassium t-butoxide in the reaction mixture in amounts from 0.1 to 1 mole percent, the reaction rate increases dramatically. A further increase in the amount of catalyst even to the molar ratio of 1/1 in the same conditions increases the yields by only 20% and is not advisable. The optimal molar ratio of rapeseed oil/t-butoxide was 1/0.01. It was found that the optimal temperature for carrying out the amidation in the presence of potassium tert-butoxide is in the range of 60–90 °C, depending on the structure of the amine used. It was revealed that the reaction also takes place at room temperature, although the yields of the target products are too low. However, the use of potassium tert-butoxide allows syntheses to be carried out under conditions in which hydroxides and other metal alkoxides are not effective. It is established that the optimal time for the amidation of rapeseed oil at the revealed temperature is on average 6–8 hours, depending on the structure of the amine. With reduced in temperature, in order to obtain a satisfactory yield, the time for synthesis should be increased.Conclusions. Studies have shown that potassium tert-butoxide exhibits a significantly greater catalytic activity in the amidation reactions of oils than other alkaline catalysts. This significantly mitigates the conditions of amidation and reduces the energy costs of the process. In addition, the data obtained make it possible to further vary the temperature and time of synthesis of vegetable oil amides, depending on the tasks.

Synthesis of quinazolin-4(3H)-ones via the reaction of isatoic anhydride with benzyl azides in the presence of potassium tert-butoxide in DMSO

In this paper, a novel method is described for the synthesis of quinazolin-4(3H)-one derivatives via the reaction of isatoic anhydride with benzyl azides in the presence of potassium tert-butoxide in DMSO. The reaction is completed after 4 h at 100°C to produce the title products in good yields.

Synthesis of New Polyheterocyclic Compounds Based on Chalcones

The reaction of methyl N-{4-[2-(2-oxo-2,3-dihydro-1H-indol-3-ylidene)acetyl]phenyl}carbamate with tosylmethyl isocyanide in tetrahydrofuran in the presence of potassium tert-butoxide led to the formation of methyl N-{4-[(4-oxo-4,5-dihydro-3H-pyrrolo[2,3-c]quinolin-1-yl)carbonyl]phenyl}carbamate. Three-component condensation of methyl N-{4-[(E)-3-R-prop-2-enoyl]phenyl}carbamates and methyl N-{4-[2-(2-oxo-2,3-dihydro-1H-indol-3-ylidene)acetyl]phenyl}carbamate with sarcosine and paraformaldehyde in boiling toluene with simultaneous removal of water by azeotropic distillation afforded methyl N-(4-{4-[4-R-1-methyl-pyrrolidin-3-yl]carbonyl}phenyl)carbamates and methyl N-[4-(1′-methyl-2-oxo-1,2-dihydrospiro[indole-3,3′-pyrrolidin]-4′-ylcarbonyl)phenyl]carbamate, respectively.

Rapeseed Oil Interesterification Reaction with Metylacetate in the Presence of BuOK/BuOH at Different Temperatures

By the investigation and comparison of different interesterification reactions at fixed reaction time researchers usually selected 1 hour as a characteristic time for the synthesis stage of industrial biodiesel production. Investigation performed in this work shows that the equilibrium of interesterification reaction mixture of rapeseed oil with methyl acetate in molar ration of 1:18 in presence of potassium tert-butoxide in tert-butanol at molar ratio to oil 0.08 at 25 °C reach the equilibrium approximately after 50 min but at 55 °C after 10 min. The equilibrium compositions of the reaction mixtures at different temperatures are different. The concentrations of TG, FAME and TA during the interesterification reaction at 25 °C obey the pseudo-first order law which do not reflect the stoichiometry of this multiple elementary steps reaction.

Synthesis of N-heterocyclic nitrenium (NHN) ions and related donor systems: Coordination with d10-metal ions

The synthesis of three new NNN- and CNC type N-heterocyclic nitrenium (NHN) ion based pincer ligands is reported from 1,3-di-(2′-bromoethyl)-triazolium bromide (5). The reaction of 5 with ammonium hexafluorophosphate followed by two equivalent of pyrrolidine/diethylamine afforded NHN ions (10a and 10b). The reaction of 5 with N-butylbenzimidazole (6) afforded nitrenium ion 7, where the chelating arms have benzimidazole based carbene carbons. In an attempt to synthesize hybrid NHN ligand containing soft tellurium donor in the chelating arm, 1-(2′-bromoethyl)-benzotriazole was first reacted with in situ generated NaTePh to afford tellurated benzotriazol (13). However, when compound 13 was treated with methyl iodide, an unexpected methylation underwent at tellurium center to afford compound 14. Reaction of 7 with Hg(OAc)2 and 10a with CuI afforded complexes 8 and 11 respectively. Both these complexes are characterized by NMR (1H, 13C), HRMS and CHN analysis. The Natural Bond Order (NBO) calculations and Atoms in Molecules (AIM) analyses sufficiently substantiate the presence of interaction between triazolium N atom with metal centre. The reaction of N,N′-disubstituted benzimidazoles, 17a–17b with in situ generated Na2Se2 in the presence of potassium tert-butoxide at room temperature afforded two novel benzimidazoline-2-chalcogenones (18a and 18b). Nitrenium ion (10a–10b), tellurated benzotriazole (13 and 14) and selone 18a are authenticated by single crystal X-ray diffraction studies.

Effect of Temperature on Interesterification of Rapeseed Oil with Methyl Acetate in Presence of BuOK/BuOH

If the interesterification reaction of rapeseed oil with methyl acetate at reactant to oil molar ratio of 18:1 in presence of potassium tert-butoxide in tert-butanol of molar ratio to oil 0.08 is conducted at a temperature of about 35 °C, reaction time for full conversion of oil is shorter than one hour, while at a temperature of 55 °C it is approximately 15 minutes. Reaction time at the desired temperature has a wide "optimal" range and cannot be an effective variable for the process optimisation. Experimental results at the temperature of 25 °C confirm the pseudo-first order of the reaction, which lowered towards the end of the reaction. The pseudo-first order rate constant was 0.63 min-1. Fuel characteristics of the interesterification reaction mixtures without purification improved with the rising of reaction temperature from 35 °C to 55 °C, however, they fail to meet the requirements of standard EN14214 for biodiesel. Methyl acetate to oil molar ratio 18:1 is too low for obtaining products with kinematic viscosity below 5.0 mm2/s.

Phenanthroline- tBuOK Promoted Intramolecular C-H Arylation of Indoles with ArI under Transition-Metal-Free Conditions.

The first example of phenanthroline- tBuOK promoted intramolecular radical C-H arylation of N-(2-iodobenzyl)indoles without involvement of transition metals has been developed. A variety of substituted 6 H-isoindolo [2, 1-a] indoles were prepared by a simple and efficient intramolecular cyclization using 1,10-phenanthroline in the presence of potassium tert-butoxide and chlorobenzene. This strategy provides a fast and versatile access to isoindolo[2,1- a]indole derivatives for the synthesis of pharmaceuticals and organic electroluminescent (EL) materials.

Safe and Metal-Free Synthesis of 1-Alkenyl Aryl Sulfides and Their Sulfones from Thiiranes and Diaryliodonium Salts

A series of 1-alkenyl aryl sulfides was synthesized from thiiranes and diaryliodonium salts in tetrahydrofuran in the presence of potassium tert-butoxide. The proposed reaction mechanism involves generation of benzynes from the diaryliodonium salts in the presence of the base. Then, nucleophilic attack of the benzynes by thiiranes, followed by hydrogen abstraction and ring opening of the generated thiiranium intermediates, provides the sulfides. These sulfides were further oxidized with performic acid to the corresponding sulfones. The current method provides a metal-free and safe method for the preparation of 1-alkenyl aryl sulfides and their sulfones.

A simple one-pot synthesis of 2,4-diaryl- 9H-pyrido[2,3-b]indoles under solvent-free conditions

Abstract A novel, simple, one-pot synthesis of 2,4-diaryl-9H-pyrido[2,3-b]indoles is described. Heating a mixture of chalcone, oxindole and ammonium acetate in the presence of potassium tert-butoxide under solvent-free conditions afforded the title compounds in good to excellent yields.

Synthesis of [1]Benzothieno[2,3-b]quinolines via Transition-Metal-Free [3+3] Annulation of Nitroarenes and Benzo[b]thiophen-3-ylacetonitrile or 3-(Phenylsulfonylmethyl)benzo[b]thiophene Carbanions

Benzo[b]thiophen-3-ylacetonitriles or 3-(phenylsulfonylmethyl)benzo[b]thiophenes react with nitrobenzene derivatives in the presence of potassium tert-butoxide and chlorotrimethylsilane to form, in good yields, 11-cyano- or 11-(phenylsulfonyl)[1]benzothieno[2,3-b]quinolines, respectively.