Zwitterionic Products Research Articles

Synthesis of new stable arylthiopyridinium N-arylimide zwitterions. Part 20: Fused azolium salts

3-Aryltetrazolopyridinium salts react with thiophenolates to afford stable arylthio substituted pyridinium N-arylimide zwitterions as red crystals. The angularly fused tetrazolo[1,5- a]quinolinium salt react analogously and also yielded a blue zwitterionic product. The new zwitterions underwent solvolysis in methanol to give N-anilinopyridones, their alkylation yielding stable N-alkyl substituted salts and their reaction with dipolarophiles results in the formation of stable cycloadducts.

Ferroelastic lattice instability during the thermally enhanced reaction of MSE

A p-dimethylaminobenzenesulfonate (MSE) polycrystalline powder is converted to the zwitterionic product p-trimethylammoniumbenzenesulfonate (ZWT) by a chemical thermally induced reaction at T= 55,5°C. Experimental results obtained by differential scanning calorimetry and 13C solid-state NMR indicate that reaction-induced stress gives rise to a ferroelastic lattice instability during the thermally enhanced solid state reaction of methyl p-dimethylaminobenzenesulfonate (MSE).

Formation of a New Zwitterionic Phosphorus Compound using Bun 3P and COS

We have recently reported the use of the crystalline tri-n-butylphosphine-carbon disulfide adduct to form a variety of heterocyclic compounds including dithiole-containing ylides,1 2-alkylidene- 1.3-dithiolanes,2 and dihydrotetrathiafulvalenes3. In particular reaction with DMAD gave the dithiole-containing ylide shown1. We now describe the corresponding reaction of triburylphosphine and carbonyl sulfide, COS, with a variety of unsaturated systems which generally takes a completely different course as shown for the example of DMAD below. The structure of the unusual zwitterionic product has been confirmed by X-ray diffraction and is shown.

Reaction of B(C6F5)3 with zirconium and hafnium benzyl diene complexes. The crystal and molecular structures of Cp″Zr(C6F5){η4-CH2CMeCHCHB(C6F5)2} and [Cp″Hf(2,3-Me2C4H4)(OEt2)][PhCH2B(C6F5)3] [Cp″ = 1,3-(SiMe3)2C5H3

The zirconium and hafnium diene complexes Cp″MCl(η4-CH2CMeCR1CH2) react with benzylmagnesium chloride to give the benzyl complexes Cp″M(η4-CH2CMeCR1CH2)(CH2Ph) (M = Zr, R1 = Me or H; M = Hf, R1 = Me) which react with B(C6F5)3 selectively under benzyl abstraction to give the zwitterionic products Cp″M(η4-diene){ηn-PhCH2B(C6F5)3}. The zirconium derivative exists as a mixture of two isomers which interchange via ring-flipping of the diene ligand, whereas the Hf compound is rigid. The isoprene analogue Cp″Zr(CH2CMeCHCH2){PhCH2B(C6F5)3} decomposes at room temperature under C–H activation and C6F5 migration from boron to zirconium to give toluene and the structurally characterised boryldiene complex Cp″Zr(C6F5){CH2CMeCHCHB(C6F5)2}. In the hafnium (but not zirconium) complexes, the [PhCH2B(C6F5)3]– anion is displaced by CH2Cl2. The addition of diethyl ether leads to the ionic compound [Cp″Hf(2,3-Me2C4H4)(OEt2)]+[PhCH2B(C6F5)3] which was characterised by X-ray diffraction.

Optical and Calorimetric Studies on the Role of Lattice Mode Softening for Assisting a Thermally Induced Solid State Reaction

The concept of phonon assisted solid-state chemical reactions is analyzed in the case of the thermal rearrangement of methyl p-dimethylaminobenzenesulfonate (MSE) to a zwitterionic product p-trimethylammoniumbenzenesulfonate (ZWT). The experimental Raman scattering reinvestigation of MSE as a function of temperature shows that mode softening does not play an important role in the thermal reaction of MSE. A series of structural phase transitions in the [90 K-300 K] temperature range is shown for the first time in the MSE crystal by calorimetry and Raman scattering.

Evidence of a lattice instability during the thermally enhanced reaction of MSE studied by calorimetry, 13C-NMR, Raman scattering and birefringence

A methyl p-dimethylaminobenzenesulfonate (MSE) polycrystalline powder or single crystal is converted to the zwitterionic product p-trimethylammonium benzenesulfonate (ZWT) by a chemical thermally induced reaction. This reaction is associated to a first-order ferroelastic phase transition in partially reacted MSE crystals. A 13C-NMR study made during the in situ transformation MSE → ZWT shows that the reaction is of first order. A strong change appears in the low-frequency Raman spectrum of MSE monocrystals when passing the transition, but only a continuous evolution in the intensity of the high-frequency modes is observed. Birefringence observations permit the evolution of the optical axes during the chemical reaction to be specified. The importance of stress induced by the reaction is discussed in relation to the ferroelastic phase transition.

Intramolecular Ion−Ion Interactions in Zwitterionic Metallocene Olefin Polymerization Catalysts Derived from “Tucked-In” Catalyst Precursors and the Highly Electrophilic Boranes XB(C6F5)2(X = H, C6F5)

The reactions of so called “tuck-in” permethyl zirconocene compounds Cp*(η5-η1-C5Me4CH2)ZrX (X = Cl (1a), C6H5 (1b), CH3 (1c)) with the highly electrophilic boranes HB(C6F5)2 and B(C6F5)3 are described. The products are zwitterionic olefin polymerization catalysts. Reactions with 1a and 1b yielded single products cleanly, but reactions with tuck-in methyl starting material 1c gave mixtures. Spectroscopic and structural studies showed that the electrophilic zirconium center in the product zwitterions was stabilized by a variety of mechanisms. In the products of reaction between 1a and 1b with HB(C6F5)2, Cp*[η5,η1-C5Me4CH2B(C6F5)2(μ-H)]ZrX (X = Cl (2a), 74%), C6H5 (2b, 62%)), the metal is chelated by a pendant hydridoborate moiety. Chloride product 2a was characterized crystallographically. In the reaction of B(C6F5)3 with 1a, the fluxional zwitterionic product Cp*[η5-C5Me4CH2B(C6F5)3]ZrCl (3a, 84%) is stabilized by a weak donor interaction between one of the ortho fluorine atoms of the −CH2B-(C6F5)3 counterion and the zirconium center (Zr−F = 2.267(5) Å). In the product of the reaction between 1b and B(C6F5)3, Cp*[η5-C5Me4CH2B(C6F5)3]ZrC6H5 (3b, 82%), a similar ortho-fluorine interaction was found in a yellow kinetic product (y-3b), which converted upon heating gently to a thermodynamic orange polymorph (o-3b) in which the zirconium center is compensated via an agostic interaction from an ortho C−H bond of the phenyl group and an interaction between the methylene group of the −CH2B-(C6F5)3 counteranion. These compounds were both characterized by X-ray crystallography. Zwitterion o-3b reacts with H2 to form the zwitterionic hydride Cp*[η5-C5Me4CH2B(C6F5)3]ZrH (4, 77%), characterized by NMR spectroscopy and X-ray crystallography to reveal a return to the ortho-fluorine mode of stabilization. Compounds 2a, 3a, o-3b, and 4 were all found to be active ethlyene polymerization catalysts; the chloride derivatives required minimal amounts of methylaluminoxane (MAO) to alkylate the zirconium center. Polymerization data are discussed in light of the structural findings for the catalysts employed.

Optical and calorimetric studies on the role of lattice mode softening in assisting a thermally enhanced solid state reaction

The concept of phonon-assisted solid-state chemical reactions is analyzed in the case of the thermal rearrangement of methyl p-dimethylaminobenzenesulfonate (MSE) to a zwitterionic product p-trimethylammoniumbenzenesulfonate. The experimental Raman scattering reinvestigation of MSE as a function of temperature shows that mode softening does not play an important role in the thermal reaction of MSE. A series of structural phase transitions in the [90–300 K] temperature range is shown in the MSE crystal by calorimetry, infrared absorption and Raman scattering.

Construction of Extended and Polymeric 1,3-Dithiolane and Tetrathiafulvalene Derivatives using Cycloaddition of Bun 3PßCS2

Cycloaddition of the adduct between Bun 3P and CS2 to strained double bonds such as in norbornene gives novel zwitterionic products such as 5. The compound 5 reacts with acetylenic dipolarophiles by cycloaddition accompanied by loss of Bun 3P to give dihydro-TTF derivatives. The corresponding reaction also occurs for norbornadiene and by using this a range of new extended sulfur-rich structures and substituted TTFs have been obtained.

REACTIONS OF A ZWITTERIONIC BENZYLIDENE COMPOUND OF THIOOXALIC ACID HYDRAZIDE AMIDE HYDRAZONE WITH C1-BUILDING BLOCKS

Abstract The zwitterionic 4-methoxybenzylidene derivative of thiooxalic acid hydrazide amide hydrazone 1 reacts with orthocarboxylic esters to 2,5-disubstituted I,3,4-thiadiazoles 2 and with carbon disulfide or 1,1′-carbonyldiimidazole to the corresponding 2,3-dihydro-1,3,4-thiadiazoles 4 and 5. The acyclic zwitterionic products 3 were obtained from 1 with aromatic acyl chlorides. X-Ray structural data of 2a and 2b are given. All compounds are characterized by spectroscopic data (1H NMR, 13C NMR, IR).

ZWITTERIONIC SPECIES FROM TRIISOPROPYLPHOSPHINE AND 2-CYANOACRYLATES: SYNTHESIS, STRUCTURE AND PROPERTIES

Abstract Triisopropylphosphine reacts with 2-cyanoacrylates with formation of the P-zwitterionic species 2a and 2b. The reaction of 2b with trimethylsilyltriflate, in the presence of traces of water, leads to the phosphonium triflate 3. 2b is alkylated at the carbon atom with methyl iodide with formation of the phosphonium iodide 4. The initially formed adducts of the zwitterionic species 2a and 2b with tosyl azide and with tosyl isocyanate are thermodynamically unstable. In the first case, the final products of the reaction are tosyl iminotriisopropylphosphine imide 6 and 2-cyanoacrylate polymers. In the second case, the reaction leads to the zwitterionic product 8, and, in the presence of traces of water, to the molecular complexes 9a and 9b. The reaction of the zwitterionic species 2a and 2b with methylisocyanate proceeds in an unusual way, resulting in the formation of the zwitterionic species 12a and 12b, as a result of the insertion of methylisocyanate into the C[sbnd]C bond of the starting zwitteri...

Isolation and HPLC Separation of Polyunsaturated Species of Rat Brain Acyl-CoA Produced During Decapitation - Ischemia

Abstract Cycloaddition of the adduct between Bun 3P and CS2 to strained double bonds such as in norbornene gives novel zwitterionic products such as 5. This dissociates to the ylide 4 so that carrying out the reaction in the presence of an aldehyde leads to a Wittig reaction to give 2-alkylidene-1,3-dithiolanes. The compound 5 reacts with acetylenic dipolarophiles by cycloaddition accompanied by loss of Bun 3P to give dihydro-TTF derivatives. Both these reaction types also occur for norbornadiene and by using this together with dialdehydes or diacetylenes a range of new sulfur-rich extended and polymeric structures have been obtained.

Flame Retardant Actions of Tris(1,3-Dichloro-2-Propyl) Phosphate in Flexible Urethane Foam

Abstract: Intermediate 4 is unstable and rearranges into 5. Substitution of chlorine atoms in 5 by dialkylamino groups gives 8 and 9. 8 reacts with TEA to give phosphaalkene 10, which slowly dimerizes into 11. Methylenephosphinophosphorane 9 shows unusual properties. It adds isocyanates to two phosphorus atoms to give zwitterionic structural isomers 12a,b. The structure of 12a was resolved by X-ray analysis. 9 reacts with azides unexpectedly giving the zwitterionic product 13. Reaction of 9 with hexafluoroacetone is unusual and leads to the ylid 14a,b. According to the X-ray data it exists in zwitterionic form 14b and displays a new type of coordination at phosphorus atom. HFA can react in a similar way with other phosphines. For example, with 15 it gives the double ylid 16.

The Development of Improved Cationic Lipids for Gene Transfer Into Cystic Fibrosis Airway Epithelial Cells

Abstract: Intermediate 4 is unstable and rearranges into 5. Substitution of chlorine atoms in 5 by dialkylamino groups gives 8 and 9. 8 reacts with TEA to give phosphaalkene 10, which slowly dimerizes into 11. Methylenephosphinophosphorane 9 shows unusual properties. It adds isocyanates to two phosphorus atoms to give zwitterionic structural isomers 12a,b. The structure of 12a was resolved by X-ray analysis. 9 reacts with azides unexpectedly giving the zwitterionic product 13. Reaction of 9 with hexafluoroacetone is unusual and leads to the ylid 14a,b. According to the X-ray data it exists in zwitterionic form 14b and displays a new type of coordination at phosphorus atom. HFA can react in a similar way with other phosphines. For example, with 15 it gives the double ylid 16.

Decomposition of 2-dialkylaminobenzoyl azides to yield isocyanates and 1,1-dialkylindazol-1-ium-3-olates

Substituted benzoyl azides normally yield the correspondingly substituted isocyanates but when a dialkylated amino group is in the 2-position, in addition to the isocyanate, the 1,1-dialkylated indazol-1-ium-3-olate is produced. The ratio of the two products is very variable depending upon the substitution in the benzene ring. Largest yields of the zwitterionic products were found when there was a substituent in the 3-position regardless of whether the substituent was electron-donating or -withdrawing.

Methylenephosphinophosphoranes. Unusual Addition Reaction in Organophosphorus Chemistry.

Abstract: Intermediate 4 is unstable and rearranges into 5. Substitution of chlorine atoms in 5 by dialkylamino groups gives 8 and 9. 8 reacts with TEA to give phosphaalkene 10, which slowly dimerizes into 11. Methylenephosphinophosphorane 9 shows unusual properties. It adds isocyanates to two phosphorus atoms to give zwitterionic structural isomers 12a,b. The structure of 12a was resolved by X-ray analysis. 9 reacts with azides unexpectedly giving the zwitterionic product 13. Reaction of 9 with hexafluoroacetone is unusual and leads to the ylid 14a,b. According to the X-ray data it exists in zwitterionic form 14b and displays a new type of coordination at phosphorus atom. HFA can react in a similar way with other phosphines. For example, with 15 it gives the double ylid 16.

Supramolekulare Phosphoryl‐Übertragungsreaktionen, vermittelt durch Amidinium‐Phosphat‐Ionenpaarkomplexe

Supramolecular Phosphoryl Transfer Reactions Mediated by Amidinium Phosphate Ion‐Pair ComplexesIn order to build up simplified synthetic models of staphylococcal nuclease two derivatives of 8‐phenylnaphthalene‐1‐carboxamidine equipped with nucleophilic side chains have been prepared (1,2). After protonation these amidinium alcohols bind phosphodiester anions via hydrogen bonds and react within the ion‐pair complexes to give zwitterionic products 27 and 28. The rate accelerations (DMF, 30°C) compared to the phosphorylation of noncharged alcohols are 2700‐fold (2) and 930‐fold (1).

Chemical reactivity within a smectic B liquid crystalline phase: A model of enzyme catalysis?

Abstract The rearrangement of allyl p-dimethylaminobenzenesulphonate (ASE) to form a zwitterionic product has already been recognized as an effective probe for the study of reactivity within the smectic B phase [4, 5, 19]. We have used deuterium NMR, linear dichroism and X-ray diffraction techniques to investigate the phase diagram of the ASE-OS35 reaction system. The partitioning of the reactant molecules between coexisting smectic, nematic and/or isotropic phases and the structural organization of the smectic catalytic host at different temperatures and reactant guest concentrations have been characterized. On the basis of these measurements, a model of ASE reactivity in smectic solvents has been developed. The reaction takes place provided that coexisting isotropic or nematic phases are present to act as a reservoir for the ASE reactant molecules prior to their entering the smectic phase; they then react and leave the smectic phase as a zwitterionic product. The analogy between this model of reactivity within smectic phases and the Michaelis-Menten enzyme processes is discussed. This relationship opens up the intriguing possibility of designing new experiments with which to investigate further liquid crystalline models of enzyme catalysis.

Synthesis and reactivity towards unsaturated organics of the diiron hydride complex [Fe2(CO)4(µ-CO)(µ-H)-(µ-PPh2)(µ-Ph2PCH2PPh2)

Ultraviolet irradiation of [Fe2(CO)6(µ-CO)(µ-dppm)]1(dppm = Ph2PCH2PPh2) with diphenylphosphine results in phosphorus–hydrogen bond cleavage to give [Fe2(CO)4(µ-CO)(µ-H)(µ-PPh2)(µ-dppm)]2. The hydride functionality in 2 readily inserts unsaturated organics. Thus reaction with ethyne yields the µ-ethenyl complex [Fe2(CO)4(µ-CHCH2)(µ-PPh2)(µ-dppm)]3. Both allene and propyne insert into 2 to give [Fe2(CO)4(µ-MeCCH2)(µ-PPh2)(µ-dppm)] which exists in two isomeric forms 4a, 4b. Both contain the 1-methylvinyl ligand but differ in the relative orientations of diphosphine and vinyl moieties. A third isomer [Fe2(CO)4(µ-HCCHMe)(µ-PPh2)(µ-dppm)]4c containing a 2-methylvinyl ligand has been isolated from the reaction of 1 with allyldiphenylphosphine via phosphorus–carbon bond cleavage at the diiron centre. Reaction of 2 with phenylethyne gives two isomeric forms of [Fe2(CO)4(µ-PhCCH2)(µ-PPh2)(µ-dppm)]5a, 5b. The nature of these isomers is deduced from 31P NMR data and an X-ray crystallographic study of one isomer of the propyne insertion product. Compound 4a crystallises in the monoclinic space group P21/c with a= 10.749(8), b= 18.122(15), c= 19.854(9)Å, β= 94.32(5)° and Z= 4. On the basis of 3492 unique reflections and 478 parameters the structure has been refined to R= 0.055 and R′= 0.054. The structure confirms the formation of a 1-methylvinyl ligand which lies trans to the diphosphine moiety but cis to the diphenylphosphido bridge. A variable-temperature 31P NMR study allows monitoring of the σ–η vinyl fluxionality in each isomer. Reaction of 2 with ethyl diazoacetate results in insertion of the nitrogen–nitrogen bond into the hydride to give the unusual zwitterionic product [Fe2(CO)4{µ-HN–NCH(CO2Et)}(µ-PPh2)(µ-dppm)]6 which is stable to prolonged thermolysis in toluene.

Alkylating properties of phosphate esters. 3. Reactivity of dialkyl 2‐(dimethylamino) ethyl phosphates

AbstractReactivity of dialkyl 2‐(dimethylamino)ethyl phosphates, (RO)2P(O)OCH2CH2NMe2 (R = Me, PhCH2) was studied in aqueous solutions. Depending on the initial substrate's concentration, reaction can involve the unimolecular fragmentation to N,N‐dimethylaziridinium dialkylphosphate, or the bimolecular isomerization to the zwitterionic derivative. The latter reaction proceeds via two consecutive SN2 steps and involves the formation of two ionic intermediates which were synthesized independently and allowed to react to give the zwitterionic product. Rate constants for the isomerization of the dimethyl ester (R = Me), as well as rate constant for the reaction between the corresponding intermediates have been determined, and the reactivity of the dimethyl ester has been compared with that of the dibenzyl derivative.