Presence Of Tetrabutylammonium Fluoride Research Articles

Hydroazidation of phenacylideneoxindoles: Synthesis of 3-substituted 3-azido-1,3-dihydro-2H-indol-2-ones via anti-electron addition

A simple synthetic strategy of 3-substituted 3-azido-1,3-dihydro-2H-indol-2-ones was realized through hydroazidation of phenacylideneoxindoles with azidotrimethylsilane under mild conditions. In the presence of tetrabutylammonium fluoride, the reaction proceeds by the anti-electron addition of N3. This azidation method of phenacylideneoxindoles is valuable in pharmaceutical synthesis and chemical biology studies because of its mild reaction conditions and simple purification of products without contamination by any transition-metal residues.

A New Strategy for the Preparation of E Isomers of Hydrazones and Anil‐Like Compounds: Thermally Stimulated Isomerization of Z Isomers of Anions

AbstractA new, simple method for the preparation of E‐isomers of hydrazones and anil‐like compounds from Z‐isomers of these compounds has been developed. In DMF, the Z‐isomers of these compounds in the presence of tetrabutylammonium fluoride (TBAF) or tetrabutylammonium acetate (TBAA) gave the corresponding N anions of the Z‐isomers, which are isomerized to the N anions of the E‐isomers even at room temperature. Upon addition of a protic solvent (H2O, or CH3OH) to this reaction mixture, the N anion of the E‐isomer was immediately quantitatively converted to the E‐isomer of the corresponding nonionic compound, which can be readily isolated by methods commonly used in the synthesis.

Metal‐free Nucleophilic α‐Azidation of α‐Halohydroxamates with Azidotrimethylsilane

AbstractA mild and metal‐free synthetic method for α‐azido carbonyl derivatives via the nucleophilic α‐azidation of α‐halohydroxamates have been established. The reactions of trimethylsilyl azide with various α‐mono‐ and disubstituted azaoxyallyl cations, generated in situ from α‐halohydroxamates, afforded a wide range of hindered mono‐ and dialkyl α‐azido carbonyl derivatives in good yields in the presence of tetrabutylammonium fluoride as a catalyst.

Fluoride-Triggered Self-Degradation of Poly(2,4-disubstitued 4-hydroxybutyric acid) Derivatives.

Self-immolative polymers are a special kind of degradable polymers that depolymerize into small molecules through a cascade of reactions upon stimuli-triggered cleavage of the polymer chain ends. This work reports the design and synthesis of a fluoride-triggered self-immolative polyester. A 2,4-disubstitued 4-hydroxy butyrate is first confirmed to quickly cyclize in solution to form a γ-butyrolactone derivative. Then, the Passerini three component reaction (P-3CR) of an AB dimer (A: aldehyde, B: carboxylic acid) with tert-butyl isocyanide or oligo(ethylene glycol) isocyanide affords two poly(2,4-disubstitued 4-hydroxybutyrate) derivatives (P2 and P3). Two silyl ether end-capped polymers (P4 and P5) are abtained from P2 and P3, and their degradation in solution is examined by NMR spectrum and size exclusion chromatography. Polymers P4 and P5 are stable in the absence of tetrabutylammonium fluoride (TBAF), while in the presence of TBAF, the molar masses of P4 and P5 gradually decrease with time together with the increase of the amount of formed 2,4-disubstitued γ-butyrolactone. The depolymerization mechanism is proposed. The first step is the fast removal of the silyl ether by fluoride. Then, the released hydroxyl group initiates the quick head-to-tail depolymerization of the polyester via intramolecular cyclization.

Enantioselective Catalytic Cyclopropanation-Rearrangement Approach to Chiral Spiroketals.

A highly enantioselective synthesis of chiral heterobicyclic spiroketals is reported via a "one-pot" cyclopropanation-rearrangement (CP-RA) cascade reaction that is sequentially catalyzed by a chiral Rh(II) catalyst and tetrabutylammonium fluoride (TBAF). Exocyclic vinyl substrates form spirocyclopropanes with tert-butyldimethylsilyl-protected enoldiazoacetates in excellent yields and with excellent enantioselectivities when catalyzed by chiral dirhodium(II) carboxylates, and following desilylation with simultaneous rearrangement in the presence of TBAF, they give (S)-spiroketals in high yields with excellent chirality retention (>95% ee).

Stille coupling for the synthesis of isoflavones by a reusable palladium catalyst in water

AbstractIsoflavones were synthesized from the reaction of 3‐bromochromone derivatives and aryltributylstannanes via Stille coupling catalyzed by a water‐soluble and reusable PdCl2(NH3)2/2,2′‐cationic bipyridyl system in aqueous solution. For prototype 3‐bromochromone, the coupling reaction was performed at 80°C for 24 hr with 2.5 mol% catalyst in water in the presence of tetrabutylammonium fluoride. After the reaction, the aqueous solution could be reused for several runs, indicating that its activity was only slightly decreased. For substituted 3‐bromochromones, the addition of NaHCO3 and a higher reaction temperature (120°C) were required to gain satisfactory outcomes. In addition, naturally occurring products, such as daidzein, could be obtained by this protocol via a one‐pot reaction.

Semiclathrate hydrate phase behaviour and structure for CH4 in the presence of tetrabutylammonium fluoride (TBAF)

Phase behaviour including phase equilibria and dissociation enthalpies and structure of double semiclathrate hydrates formed with tetrabutylammonium fluoride (TBAF) + CH4 were measured to evaluate the performance of TBAF for hydrate based industrial applications. The phase equilibria and the dissociation enthalpies for TBAF + CH4 semiclathrate hydrate (SCH) with (0.02–0.15) salt mass fraction were obtained by employing the isochoric pressure-search method and calculated from the experimental data with Clausius-Clapeyron equation, respectively. A confocal Raman spectrometer was applied to analyze the structure of (TBAF + CH4) SCHs. Data showed that TBAF strongly enhanced the stability of CH4 hydrates by increasing the equilibrium temperature at a given pressure. The Raman spectra revealed that small 512 cages of TBAF hydrates could trap CH4 molecules. In particular, the Raman spectra of double TBAF + CH4 SCHs, as compared with those of pure TBAF SCHs, indicated that the large cages which already trapped the cation of TBAF also had the possibility of encaging CH4 molecules at low salt concentrations (<0.12 mass fraction).

Synthesis of 2-(1-Oxo-2,3-Dihydro-1H-Pyrrolizin-2-yl)-2-(Aryl)Acetonitrile Derivatives Via Michael Addition of Trimethylsilyl Cyanide

Several 2-aryl-2-(1-oxo-2,3-dihydro-1 H-pyrrolizin-2-yl)acetonitrile derivatives were synthesised by Michael addition of ( E)-2-arylidene-2,3-dihydro-1 H-pyrrolizin-1-ones with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride in moderate yields. The structures of all of the products were fully characterised by NMR, IR and high-resolution mass spectrometry, together with X-ray crystallographic analysis.

Synthesis of 2H-Chromene-4-Carbonitriles Via Trimethylsilyl Cyanide

A number of 2-aryl-2 H-chromene-4-carbonitriles were synthesised by cyanation of 2-aryl-3-nitro-2 H-chromenes using trimethylsilyl cyanide (TMSCN) in the presence of tetrabutylammonium fluoride (TBAF) in moderate yields via a Michael addition/elimination pathway. The structures of all the products were characterised thoroughly by NMR, IR and HRMS spectroscopy and X-ray crystallographic analysis.

Regioselective Synthesis of 2,5-Disubstituted Pyrroles via Stepwise Iododesilylation and Coupling Reactions

A new protocol has been developed for the regioselective preparation of 2,5-disubstituted pyrroles. This approach is based on a stepwise iododesilylation and a subsequent coupling reaction, involving a 6-step pathway starting from the simplest pyrrole. A variety of 2,5-disubstituted pyrrole derivatives are accessible in moderate to good yields. In this study, the protection group for the pyrrole nitrogen is carefully chosen and N,N-dimethylaminosulfonyl is the final choice, which facilitates the subsequent double lithiation and makes the pyrrole moiety more stable. However, the attempted removal of this group fails under several different conditions. Instead, unexpected dimethylaminosulfonyl migration to the β-position of the pyrrole ring in the presence of tetrabutylammonium fluoride is observed.

Synthesis of 2-Cyano-3-Nitroporphyrin Derivatives with Silyl Cyanide

2-Cyano-3-nitroporphyrin derivatives were synthesised by the reaction of 2-nitroporphyrin with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride with moderate yields. The reaction took place regioselectively on the 3-position carbon of the porphyrins, which was confirmed by X-ray analysis.

Synthesis of 3-cyano-N-confused porphyrin derivatives by silyl cyanide

3-Cyano- N-confused porphyrin derivatives were synthesised by the reaction of N-confused porphyrin with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride in moderate yield. The reaction took placed regioselectively in the 3-position carbon of the inverted pyrrole of N-confused porphyrins.

STEREODIRECTED SYNTHESIS OF (Е)- AND (Z)-ISOMERS OF 8-CHLOROOCT-7-EN-4-ONE

For citation:Shakhmaev R.N., Sunagatullina A.Sh., Alieva R.M., Zorin V.V. Stereodirected synthesis of (Е)- and (Z)-isomers of 8-chlorooct-7-en-4-one. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 1. P. 40-44. Reaction of ethyl 3-oxohexanoate with equimolar amounts of (E)- or (Z)-1,3-dichloro-propene under phase transfer catalysis conditions in the presence of K2CO3 afforded the corresponding monosubstituted (E)- or (Z)-isomers of ethyl 2-(3- chloroprop-2-en-1-yl)-3-oxohexa-noate and considerable amount of disubstituted derivatives (30-40%). In order to increase yields of monosubstituted derivatives we carried out research to test the known methods of selective monoalkylation of β-dicarbonyl compounds with respect to test substrates. Alkylation of ethyl 3-oxohexanoate in the presence of tetrabutylammonium fluoride and cobalt salts have not led to a significant increase in reaction selectivity, but in the reaction in solid in the absence of solvent the formation of disubstituted products is not practically observed. In the reaction of ethyl 3-oxo-hexanoate with (E)- or (Z)-isomers of 1,3-dichloropropene on the surface of Al2O3 impregnated with t-BuOK monosubstituted products are formed with the yields of 81 and 79%, respectively. Solid phase alkylation proceeds with high stereoselectivity, isomeric purity of target products are greater than 99%. Standard methods of monoalkylated ketoesters decarboxylation under acidic or basic conditions lead to low yields of the corresponding chlorovinyl ketones, best results are obtained at decarboxylation of (E)- or (Z)-isomers of ethyl 2-(3-chloroprop-2-en-1-yl)-3-oxohexa-noate in slightly modified Krapcho conditions. Carrying out the reaction in N-metrhylpirroli-dinone at a temperature of 130-140 °C in the presence of 3 eq. LiCl leads to (E)- and (Z)-isomers of 8-chlorooctyl-7-ene-4-one with 81 and 77% yields, respectively, and an isomeric purity of ~ 99%.

Exploring allene chemistry using phosphorus-based allenes as scaffolds

Abstract In this paper, we review some of our results on cycloaddition and cyclization reactions of allenylphosphonates/and allenyl phosphine oxides. Thus nitro-substituted propargylic alcohols react with P(III)–Cl substrates to lead to unprecedented phosphono-benzazepines or -hydroxyindolinones. A similar reaction using a higher stoichiometry of P(III)–Cl precursor has led to the first observation of spontaneous resolution by crystallization in allene chemistry. In the reaction of these phosphorus based allenes with diphenyl isobenzofuran (DPBF), depending on the substituents, both [α, β] and [β, γ]-cycloaddition products are formed. Extension of this work to sulfur based allenes and leading to a new [4+2] cycloadduct with DPBF is reported. A novel cyclization reaction of a functionalized allenylphosphine oxide with diethylamine leading to 3-diethylamino-4-diphenylphosphinoyl-1-naphthol is discovered. Base-catalyzed reactions of allenylphosphonates with 2-substituted benzaldehdes lead to novel thiochromans, chromenes, and quinolines. Allenylphosphonates undergo phosphonylation in the presence of tetrabutyl ammonium fluoride (TBAF). Vinyl azides derived from allenylphosphonates undergo thermolysis to form bis-phosphonopyrazines. [Pd]-catalyzed reactions of allenes with 2-iodophenols, 2-iodobenzyl alcohol and 3-iodo-indole-2-carboxylic acids lead to a variety of benzofurans, benzopyrans and benzopyranones, respectively.

Tandem Aryne-Capture/Sigmatropic Rearrangement as a Metal-Free Entry to Functionalized N-Aryl Pyrrolidines.

We report a new method for the synthesis of novel N-aryl proline analogues. By reacting an aryne precursor with N-(2-malonyl) tetrahydropyridines in the presence of tetrabutylammonium fluoride (TBAF), a tandem aryne-capture/anion isomerisation/[2,3]-sigmatropic rearrangement is induced, leading to good yields of 3-substituted N-aryl-2-acylpyrrolidines. These products are known subunits of biological probes, sensors and drug-like fragments, and are not easily accessed directly by other methods. The reaction is also notable as the first [2,3]-rearrangement of cyclic ammonium ylides at room temperature.

A (Borylmethyl)silane Bearing Three Hydrolyzable Groups on Silicon: Synthesis via Iridium-Catalyzed C(sp3)–H Borylation and Conversion to Functionalized Siloxanes

An iridium-catalyzed C(sp3)–H borylation of X3SiMe (X = hydrolyzable group) was established. A trialkoxy(methyl)silane bearing sterically demanding neopentyloxy groups (X = neopentyloxy) underwent C–H borylation at the methyl group on silicon, giving (borylmethyl)tris(neopentyloxy)silane in 70% isolated yield. The choice of the hydrolyzable group X was the key to efficient and chemoselective C–H borylation; trialkoxy(methyl)silanes bearing sterically less demanding alkoxy groups (X = ethoxy, n-butyloxy, and isobutyloxy) suffered from C–H activation at the alkoxy groups, and trichloro(methyl)silane (X = Cl) failed to react. A trimethylsiloxy group could substitute the neopentyloxy groups of the borylated product by the reaction of trimethylsilanol in the presence of tetrabutylammonium fluoride.

Autoxidation/Aldol Tandem Reaction of 2-Oxindoles with Ketones: A Green Approach for the Synthesis of 3-Hydroxy-2-Oxindoles.

In the presence of tetrabutylammonium fluoride and molecular sieves (MS) 4 Å in DMF, an efficient autoxidation reaction of 2-oxindoles with ketones under air at room temperature has been developed. This approach may provide a green, practical, and metal-free protocol for a wide range of biologically important 3-hydroxy-3-(2-oxo-alkyl)-2-oxindoles.

ChemInform Abstract: Straightforward Synthesis of 1,2‐Dicyanoalkanes from Nitroalkenes and Silyl Cyanide Mediated by Tetrabutylammonium Fluoride.

AbstractA straightforward synthesis of 1,2‐dicyanoalkanes by reacting nitroalkenes with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride is described.

ChemInform Abstract: Electrogenerated Acetonitrile Anions/Tetrabutylammonium Cations: An Effective Catalytic System for the Synthesis of Novel Chromeno[3′,4′:5,6]pyrano[2,3‐d]pyrimidines.

Abstract An efficient and convenient synthesis of novel chromeno[3′,4′:5,6]pyrano[2,3- d ]pyrimidines is described, using the electrogenerated anion of acetonitrile as the base in the presence of tetrabutylammonium fluoride as an effective supporting electrolyte in a one-pot, three-component condensation of barbituric acid, an aromatic aldehyde or isatin, and 4-hydroxycoumarin. The reaction is carried out in an undivided cell containing an iron electrode as the cathode and a Pt electrode as the anode, at a constant current at room temperature.

Straightforward synthesis of 1,2-dicyanoalkanes from nitroalkenes and silyl cyanide mediated by tetrabutylammonium fluoride.

A straightforward synthesis of 1,2-dicyanoalkanes by reacting nitroalkenes with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride is described. The reaction proceeds through a tandem double Michael addition under mild conditions. Employing the hypervalent silicate generated from trimethylsilyl cyanide and tetrabutylammonium fluoride is essential for achieving this transformation. Mechanistic studies suggest that a small amount of water included in the reaction media plays a key role. This protocol is applicable to various types of substrates including electron-rich and electron-deficient aromatic nitroalkenes, and aliphatic nitroalkenes. Moreover, vinyl sulfones were found to be good alternatives, particularly for electron-deficient nitroalkenes. The broad substrate scope and functional group tolerance of the reaction makes this approach a practical method for the synthesis of valuable 1,2-dicyanoalkanes.