1449-46-3Relevant academic research and scientific papers
Kinetics and mechanistic investigation of epoxy-anhydride compositions cured with quaternary phosphonium salts as accelerators
Amirova, Lyaysan R.,Burilov, Alexander R.,Amirova, Liliya M.,Bauer, Ingmar,Habicher, Wolf D.
, p. 1088 - 1097 (2016)
Mechanism and curing kinetics of bisphenol A epoxy resin-iso-methyltetrahydrophthalic anhydride compositions using quaternary phosphonium salts as accelerators were investigated by differential scanning calorimetry (DSC) and electrospray mass-spectrometry (ESI-MS). The DSC method was applied to investigate curing kinetics and apparent activation energy values for the overall curing process. The DSC results showed that some of the phosphonium salts lead to a lower activation energy, that means they are more effective accelerators for the curing of epoxy-anhydride systems. The mechanism of curing was studied by ESI-MS using the model reaction of epichlorohydrin (E) with phthalic anhydride (PA) in the presence of phosphonium salts or 2-methylimidazole. Products containing the alkyl moiety of the phosphonium salt in form of alkyl esters could be identified. This suggests that the phosphonium salts activate the anhydride by electrophilic attack.
Cis alkenes stabilized by intramolecular sulphur?π interactions
Zhao, Xiaolei,Zheng, Wei,Zhang, Yi,Huang, Wei
, p. 814 - 817 (2020)
A series of alkenes with bistable isomers were obtained containing a thiophene/azoheteroaryl backbone. Visible light and heat-induced reversible cis ? trans isomerizations were evidenced by UV-Vis and 1H NMR spectra. The stabilization of cis alkenes was attributed to intramolecular sulphur?π (S?π) interactions, which were further supported by theoretical calculations.
Investigating Variation of the Pnicogen Nucleophilic Heteroatom on Ionic Liquid Solvent Effects in Bimolecular Nucleophilic Substitution Processes
Schaffarczyk McHale, Karin S.,Haines, Ronald S.,Harper, Jason B.
, p. 534 - 539 (2019)
A series of nucleophiles containing Group 15 nucleophilic heteroatoms has been used to expand and develop the current understanding of ionic liquid solvent effects on bimolecular nucleophilic substitution processes. It was found that when using arsenic-, antimony- and bismuth-based nucleophiles, rate constant enhancement was observed for all solvent compositions containing ionic liquids. This rate constant enhancement was driven by ionic liquid/transition state interactions, which contrasts with previous studies on earlier Group 15 nucleophiles. This study provides a holistic understanding and augments the predictive framework for the effects of ionic liquids on bimolecular nucleophilic substitution processes, with the potential for these periodic trends to be broadly applied.
Synthesis and crystal structures of (Benzyl)triphenylphosphonium Bromides, [C6H5-CH2P(C6H5) 3]+Br- and [C6H5-CH2P(C6H5) 3]+Br3-
Hübner,Wulff-Molder,Vogt,Meisel
, p. 1321 - 1324 (1997)
(Benzyl)triphenylphosphonium bromide, [C6H5-CH2P(C6H5) 3]+Br- (CH2Cl2) (1) has been prepared by the reaction of triphenylphosphine with benzylbromide and its structure determined. The colorless crystals are triclinic, space group P1, Z = 2, a = 976.0(3), b = 1069.0(3), c = 1226.1(4) pm. α = 94.13(3), β = 104.70(3), γ = 100.14(3)°. The lattice contains Br- anions and [C6H5-CH2P(C6H5) 3]+ cations. [C6H5-CH2P(C6H5) 33]Br3 (2) has been obtained by treating compound 1 with equimolar quantities of elemental bromine in methylene chloride solution. The red crystals of 2 are monoclinic, space group P21/c, Z = 4, a = 917.9(2), b = 1022.6(2), c = 2573.6(5) pm, β = 99.11(2)°, and comprise[C6H5-CH2P(C6H 5)3]+ cations and linear, slightly asymmetrical Br3- anions with bromine-bromine distances of 246.19(11) and 263.69(11) pm.
Functionalized Cyclopropanes as Versatile Intermediates for the Diversity-Oriented Synthesis of γ-Lactones, γ-Lactams and δ-Lactams
Maximiano, Adrielle P.,Ramos, Giovana S.,Marques, Marcelo V.,Sá, Marcus M.
, (2021)
A two-step procedure for the preparation of cyclopropanecarboxaldehyde-1,1-diester from a γ,δ-epoxyester and its synthetic versatility are described herein. The epoxide ring-opening/cyclopropanation process occurs in the presence of Mg(ClO 4) 2under heating, resulting in cyclopropanemethanol-1,1-diester in 65% yield. A mild TEMPO-mediated oxidation of this substrate readily generated the corresponding aldehyde in 75% yield, which was applied in the one-pot synthesis of four cyclopropylidene-γ-lactams and three δ-lactams. In addition, vinylcyclopropanes were obtained through the Wittig reaction of the aldehyde with phosphonium salts and used as precursors for tetrahydrofurans.
Photochemical Synthesis and Electronic Properties of Extended Corannulenes with Variable Fluorination Pattern
Halilovic, Dzeneta,Budanovi?, Maja,Wong, Zeng R.,Webster, Richard D.,Huh, June,Stuparu, Mihaiela C.
, p. 3529 - 3536 (2018)
The first family of extended and fluorinated corannulenes is prepared through a highly efficient and modular synthetic strategy. In this strategy, corannulene aldehyde could be combined with the fluorine-carrying phosphonium ylides to furnish stilbene-like vinylene precursors. A photochemically induced oxidative cyclization process of these precursors gives rise to the fluorinated and curved polycyclic aromatic hydrocarbons. A UV-vis absorption study shows that aromatic extension results in a bathochromic shift of about 12 nm. Fluorination further shifts the absorption spectrum to the red region, and a maximum shift of about 22 nm is detected for a compound carrying two trifluoromethyl groups. A cyclic and square-wave voltammetry investigation reveals that the extension of the corannulene scaffold increases the reduction potential by 0.11 V. Placement of fluorine or trifluoromethyl groups further enhances the electron affinities. In this regard, the presence of one trifluoromethyl group equals the effect of three aromatic fluorine atoms. Molecules with two trifluoromethyl groups, meanwhile, exhibit the highest reduction potentials of -1.93 and -1.83 V. These values are 0.37 and 0.46 V higher than those of the parental corannulene and demonstrate the utility of the present design concept by efficiently accessing effective electron acceptors based on the buckybowl motif.
Catalyst-free room-temperature iClick reaction of molybdenum(II) and tungsten(II) azide complexes with electron-poor alkynes: Structural preferences and kinetic studies
Schmid, Paul,Maier, Matthias,Pfeiffer, Hendrik,Belz, Anja,Henry, Lucas,Friedrich, Alexandra,Sch?nfeld, Fabian,Edkins, Katharina,Schatzschneider, Ulrich
, p. 13386 - 13396 (2017)
Two isostructural and isoelectronic group VI azide complexes of the general formula [M(η3-allyl)(N3)(bpy)(CO)2] with M = Mo, W and bpy = 2,2′-bipyridine were prepared and fully characterized, including X-ray structure analysis. Both reacted smoothly with electron-poor alkynes such as dimethyl acetylenedicarboxylate (DMAD) and 4,4,4-trifluoro-2-butynoic acid ethyl ester in a catalyst-free room-temperature iClick [3 + 2] cycloaddition reaction. Reaction with phenyl(trifluoromethyl)acetylene, on the other hand, did not lead to any product formation. X-ray structures of the four triazolate complexes isolated showed the monodentate ligand to be N2-coordinated in all cases, which requires a 1,2-shift of the nitrogen from the terminal azide to the triazolate cycloaddition product. On the other hand, a 19F NMR spectroscopic study of the reaction of the fluorinated alkyne with the tungsten azide complex at 27 °C allowed detection of the N1-coordinated intermediate. With this method, the second-order rate constant was determined as (7.3 ± 0.1) × 10-2 M-1 s-1, which compares favorably with that of first-generation compounds such as difluorocyclooctyne (DIFO) used in the strain-promoted azide-alkyne cycloaddition (SPAAC). In contrast, the reaction of the molybdenum analogue was too fast to be studied with NMR methods. Alternatively, solution IR studies revealed pseudo-first order rate constants of 0.4 to 6.5 × 10-3 s-1, which increased in the order of Mo > W and F3C-CC-COOEt > DMAD.
Supramolecular Recognition of Quaternary Phosphonium Cations
Walsh, Mark P.,Kitching, Matthew O.
, (2021/12/06)
The modes of supramolecular recognition of quaternary phosphonium cations mediated by 1,1′-bi-2-naphthol (BINOL) are identified and characterized. In contrast to our previous work on ammonium cations, the recognition of the quaternary phosphonium cations via the formation of a PR4+·Br–·BINOL ternary complex was found to be mediated by a hydrogen bond from an α-carbon center of the phosphonium cation, encapsulation within a continuous hydrogen bond network between the halide–BINOL network, or a combination of these effects working in tandem. The solid state structures of these ternary complexes were analyzed by X-ray crystallography, aided by Hirshfeld surface analysis, to confirm the presence of characteristic intermolecular interactions for the identified modes. In all cases, the quaternary phosphonium cation acts as a hydrogen bond donor (HBD) in these supramolecular interactions, and thus this is the key to the recognition process with BINOL. The characterization of such mechanisms offers insight into the supramolecular and crystal engineering communities in the future design of agents capable of the supramolecular recognition of phosphonium cations and their abstraction from the solution phase.
Synthesis of Indoles by Reductive Cyclization of Nitro Compounds Using Formate Esters as CO Surrogates
Ahmed Fouad, Manar,Ferretti, Francesco,Formenti, Dario,Milani, Fabio,Ragaini, Fabio
supporting information, p. 4876 - 4894 (2021/09/20)
Alkyl and aryl formate esters were evaluated as CO sources in the Pd- and Pd/Ru-catalyzed reductive cyclization of 2-nitrostyrenes to give indoles. Whereas the use of alkyl formates requires the presence of a ruthenium catalyst such as Ru3(CO)12, the reaction with phenyl formate can be performed by using a Pd/phenanthroline complex alone. Phenyl formate was found to be the most effective CO source and the desired products were obtained in excellent yields, often higher than those previously reported using pressurized CO. The reaction tolerates many functional groups, including sensitive ones like a free aldehydic group or a pendant pyrrole. Detailed experiments and kinetic studies allow to conclude that the activation of phenyl formate is base-catalyzed and that the metal doesn't play a role in the decarbonylation step. The reactions can be performed in a single thick-walled glass tube with as little as 0.2 mol-% palladium catalyst and even on a 2 g scale. The same protocol can be extended to other nitro compounds, affording different heterocycles.
One-Step Synthesis of Triphenylphosphonium Salts from (Het)arylmethyl Alcohols
Abaev, Vladimir T.,Chalikidi, Petrakis N.,Demidov, Oleg P.,Gutnov, Andrey V.,Magkoev, Taimuraz T.,Trushkov, Igor V.,Uchuskin, Maxim G.
, p. 9838 - 9846 (2021/07/28)
Two approaches for the synthesis of substituted phosphonium salts from easily available benzyl alcohols and their heterocyclic analogs have been developed. The developed protocols are complementary: the direct mixing of alcohol, trimethylsilyl bromide, and triphenylphosphine in 1,4-dioxane followed by heating at 80 °C was found to be more efficient for acid-sensitive substrates, such as salicyl or furfuryl alcohols as well as secondary benzyl alcohols, while a one-pot procedure including sequential addition of trimethylsilyl bromide and triphenylphosphine gave higher yields for benzyl alcohols bearing electroneutral or electron-withdrawing substituents.
