Acetonitrile Yields Research Articles

A Novel Method for the Deoxygenation of Sulfoxides with the PPh3/Br2/CuBr System

Abstract It was found that the combination of PPh3/Br2/CuBr was an effective promoter for the deoxygenation of sulfoxides and gave the corresponding sulfides in excellent yield in acetonitrile under refluxing conditions. It is worth mentioning that this reagent system is chemoselective, tolerating various functional groups such as carbon–carbon double bond and ketone.

Synthesis, Structure, and Magnetic Properties of [(CH3CN)5V−O−V(CH3CN)5][BF4]4

The reaction of vanadium(III) acetylacetonate with HBF4 in acetonitrile yields [(CH3CN)5V-O-V(CH3CN)5][BF4]4, a material that serves as a convenient precursor to other [V-O-V]4+ species such as [(bipy)2(CH3CN)V-O-V(CH3CN)(bipy)2][BF4]4 (bipy=2,2'-bipyridine). Single-crystal X-ray diffraction shows that the V-O-V linkage of [(CH3CN)5V-O-V(CH3CN)5]4+ is linear. An Evans method measurement of the solution-phase magnetic susceptibility indicates strong ferromagnetic coupling between the vanadium centers. Magnetic susceptibility (chi) and magnetization (M(H)) data for a powdered sample and for a single crystal oriented with its V-O-V axis parallel to the applied field were measured over 1.8-300 K. The results suggest that the V(III) centers are ferromagnetically coupled with J approximately 72 K (approximately 50 cm(-1)) yielding a ground state with a total spin Stotal=2. Theoretical fit to the M(H) plot for the single crystal yielded g||=2.01+/-0.01 and the zero-field splitting parameter D=0.60+/-0.04 K (0.42+/-0.03 cm(-1)). EPR measurements at 34 and 101.6 GHz are consistent with the Stotal=2 ground state and yield g||=1.9825, g perpendicular=1.9725 and D=0.57+/-0.03 K.

A New and Efficient Method for the Protection of Alcohols and Phenols by Using Hexamethyldisilazane in the Presence of Anhydrous Ferric Chloride under Mild Reaction Conditions

Alcohols and phenols are protected with hexamethyldisilazane in the presence of anhydrous ferric chloride in good to excellent yields in acetonitrile. This method is highly selective for the conversion of primary alcohols in the presence of secondary and tertiary alcohols and also for conversion phenols.

Aza-Morita–Baylis–Hillman reaction of ethyl (arylimino)acetate with methyl vinyl ketone and ethyl vinyl ketone

Aza-Morita–Baylis–Hillman (aza-MBH) reaction of ethyl (arylimino)acetate with methyl vinyl ketone and ethyl vinyl ketone has been investigated. We found that aza-MBH adducts 1 could be formed in the presence of DABCO (30 mol %) and the corresponding adducts 2 could be obtained in the presence of PPh 3 (30 mol %) in moderate to good yields in acetonitrile under mild conditions, respectively.

Selective Syntheses of Benzoxazoles and N‐(2‐Hydroxyaryl)pyrrolidin‐2‐ones from the Corresponding Cyclopropyl Amides with PPh3/CX4.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Dinuclear iron, ruthenium and cobalt complexes containing 1,4-dimethyl-1,4,7-triazacyclononane ligands as well as carboxylato and oxo or hydroxo bridges

The reaction of 1,4-dimethyl-1,4,7-triazacyclononane (L–Me 2) with FeSO 4 · 7H 2O in aqueous ethanol gives, in the presence of sodium carboxylates, hydrogen peroxide, sodium hydroxide and KPF 6, the dinuclear Fe(III)–Fe(III) complex cations [(L–Me 2) 2Fe 2(O)(OOCR) 2] 2+ (R = H: 1, R = CH 3: 2, R = C 6H 5: 3), which crystallise as the hexafluorophosphate salts. The corresponding reaction with RuCl 3 · nH 2O does not work, however, the analogous Ru(III)–Ru(III) complex [(L–Me 2) 2Ru 2(O)(OOCCH 3) 2] 2+ ( 5) can be synthesised by reacting Ru(dmso) 4Cl 2 with L–Me 2, HCl and air in refluxing ethanol, followed by addition of sodium acetate, the mononuclear intermediate (L–Me 2)RuCl 3 · H 2O ( 4) being also isolated and characterised. The reaction of L–Me 2, sodium acetate, hydrogen peroxide and triethylamine with CoCl 2 · 6H 2O in acetonitrile yields, however, the hydroxo-bridged Co(III)–Co(III) complex [(L–Me 2) 2Co 2(OH)(OOCCH 3) 2] 3+ ( 6). The molecular structures of 2, 5 and 6, solved by single-crystal X-ray structure analyses of the hexafluorophosphate salts, reveal for the orange crystals of [ 2][PF 6] 2 a Fe–Fe distance of 3.104(1) Å, for the purple crystals of [ 5][PF 6] 2 a Ru–Ru distance of 3.230(1) Å, and for the violet crystals of [ 6][PF 6] 3 · (CH 3) 2CO a Co–Co distance of 3.358(1) Å. All six complexes show catalytic activity for the oxidation of isopropanol with hydrogen peroxide in water to give acetone in the presence of ascorbic acid as co-catalyst.

Selective syntheses of benzoxazoles and N-(2-hydroxyaryl)pyrrolidin-2-ones from the corresponding cyclopropyl amides with PPh 3/CX 4

Benzoxazoles 2 can be smoothly synthesized by treatment of starting materials of N-(2-hydroxyaryl) cyclopropyl amides 1 with PPh 3/CCl 4 in acetonitrile in good yields. When PPh 3/CBr 4/MS 4 Å was used in the reaction system, the corresponding ring-expanding products 3 were obtained in moderate to good yields in acetonitrile at 80 °C. Using DCE as a solvent in this reaction, the corresponding 2-(3-chloropropyl)benzoxazoles 5 were obtained as major products.

An Efficient Method for the Protection of Alcohols and Phenols by Using Hexamethyldisilazane in the Presence of Cupric Sulfate Pentahydrate under Neutral Reaction Conditions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of asymmetricallymeso-substituted porphyrins bearing amino groups as potential cationic photodynamic agents

Novel asymmetrically meso-substituted porphyrins bearing amino groups have been synthesized as precursors of cationic photodynamic agents. The amphiphilic character of these porphyrins was increased by the presence of a high lipophilic trifluoromethyl group. Different patterns of porphyrin structures were obtained from meso-4-[(3- N , N -dimethylaminopropoxy)phenyl] dipyrromethane 1, which was formed by the condensation of 4-(3- N , N -dimethylaminopropoxy) benzaldehyde with a large excess of pyrrole. This reaction takes place at high temperature with a yield of 59%. This reaction was also attempted under acid-catalyzed condensation at room temperature. However, under these conditions, the amino group reduces the catalyst and the reaction does not take place. To obtain porphyrins, dipyrromethane 1 was condensed with aldehydes in the presence of trifluoroacetic acid ( TFA ) under different conditions. First, 1 reacted with 4-(3- N , N -dimethylaminopropoxy)benzaldehyde in dichloromethane catalyzed by TFA (∼4 times TFA /1 molar ratio) to obtain 6.2% of 5,10,15,20-tetrakis(4-[3- N , N -dimethylaminopropoxy]phenyl)porphyrin ( A4-porphyrin). Under similar conditions, reaction of 1 with 4-(trifluoromethyl)benzaldehyde produces 5,15-di(4-[3- N , N -dimethylaminopropoxy]phenyl)-10,20-di(4-trifluoromethylphenyl)porphyrin ( A2B2- porphyrin ) with a 4.8% yield. This procedure also yields a mixture of porphyrins, which were formed due to acidolysis of 1. When a minor amount of TFA was used in acetonitrile, the yield of A2B2-porphyrin was very poor (∼0.4%). On the other hand, condensation of 1 with 4-trifluoromethylbenzaldehyde and 4-(3- N , N -dimethylaminopropoxy)benzaldehyde catalyzed by TFA (∼2 times TFA /1 molar ratio) in acetonitrile yields 9.3% of 5-(4-trifluoromethylphenyl)-10,15,20-tris(4-[3- N , N -dimethylaminopropoxy]phenyl)porphyrin ( A3B-porphyrin ). A2B2and A4porphyrins were also isolated with 6.0 and 2.0%, respectively. Finally, exhaustive methylation of amino porphyrins produces cationic sensitizers (>94% yield). Absorption and fluorescence spectroscopic studies of these sensitizers were compared in N , N -dimethylformamide. In these porphyrins, the cationic centers are isolated from the porphyrin ring by a propoxy bridge. Thus, the cationic charges have minimal influence on the photophysical properties of the sensitizers. In addition, this chain provides a higher mobility of the charge, which could facilitate interaction with the outer membrane of the Gram-negative bacteria. These amphiphilic cationic porphyrins are promising photosensitizers with potential applications in bacterial inactivation by photodynamic therapy.

Photochemistry of the alkaloids eudistomin N (6-bromo-nor-harmane) and eudistomin O (8-bromo-nor-harmane) and other bromo-β-carbolines

The UV-absorption, fluorescence excitation and emission spectra of the alkaloids eudistomin N (6-bromo-nor-harmane) and eudistomin O (8-bromo-nor-harmane) were described. In order to perform a comparative analysis, we also studied other bromo-β-carbolines and the corresponding non-substituted-carboline. Thus, 6-bromo-, 8-bromo-, 6,8-dibromo-, 3,6-dibromo- and 3,6,8-tribromo-derivatives of nor-harmane, harmane and harmine were studied. These studies were performed in EtOH and in EtOH + 1% perchloric acid solutions (pa). Furthermore, fluorescence quantum yields ( ϕ f) in acetonitrile and acetonitrile + 1% perchloric acid solutions at 298 K were measured. The HOMO and LUMO energy, the positions ( λ max) and oscillator strength ( f) of the 1S 1 ← 1S 0 band for all the neutral and protonated β-carbolines studied was calculated and compared with the experimental data. The p K a values in aqueous solution for eudistomin N and O (6-bromo- and 8-bromo-nor-harmane), for 6-bromo-, 8-bromo- and 6,8-dibromo-harmane, and for 6-bromo- and 8-bromo-harmine were spectrophotometrically measured ( p K a ( H 2 O ) ) . The change of the acid–base character of these compounds on going from the ground state (p K a) to the first electronic excited singlet state ( p K a ∗ ) as Δ p K a = p K a ∗ - p K a = 0.625 Δ ν ¯ / T , in ethanol solution at 298 K were calculated (Δp K a(EtOH)). Proton affinities (PA) for all the compounds studied defined as minus the enthalpy change of the reaction M + H + → MH + (gas state) were calculated. Basicity relative to pyridine (Δ H rPy) defined as the enthalpy change of the isodesmic reaction MH + + Py → M + PyH + (gas state) was also calculated. The effect of bromine as substituent on the properties of the β-carboline moiety in nor-harmane, harmane and harmine is discussed.

An Efficient Method for the Protection of Alcohols and Phenols by Using Hexamethyldisilazane in the Presence of Cupric Sulfate Pentahydrate under Neutral Reaction Conditions

Alcohols and phenols are protected with hexamethyldi­silazane in the presence of cupric sulfate pentahydrate in good to excellent yields in acetonitrile. The method is highly selective for the conversion of primary alcohols in the presence of secondary and tertiary alcohols as well as phenols.

A General and Mild Ullmann‐Type Synthesis of Diaryl Ethers.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Platinum(II) and palladium(II) complexes containing a mixed donor `P 2N' multidentate ligand

The `P 2N' mixed donor ligand 2-(diphenylphosphino)- N-[2-(diphenylphosphino)benzylidene]benzeneamine (PNCHP) reacts with [MCl 2(1,5-cyclooctadiene)] and [M(CH 3)Cl(1,5-cyclooctadiene)] to give the complexes [M(PNCHP-κ 3 P, N, P)Cl]Cl (M=Pt or Pd) and [Pd(PNCHP-κ 3 P, N, P)(CH 3)]Cl, respectively. The ionic chloride can be exchanged with BF 4 − by reaction with AgBF 4. Abstraction of the covalent chloride with AgBF 4 in the presence of acetonitrile yields [Pt(PNCHP-κ 3 P, N, P)(CH 3CN)] 2+. The acetonitrile ligand of this dication can be substituted with a variety of ligands to afford complexes of the type, [Pt(PNCHP-κ 3 P, N, P)L] 2+ (L=the monodentate ligands: triphenylphosphine, 2-picoline, 3-picoline or the chelate ligands: 1,10-phenanthroline, 2,2 ′-bipyridine, bis(diphenylphosphino)ethane, 2,2 ′:6 ′,2″-terpyridine). The latter ligands all bind in a bidentate fashion to give five-coordinate complexes. The compounds have been characterised by spectroscopic and analytical means. The single crystal structures of the four-coordinate complexes, [Pt(PNCHP-κ 3 P, N, P)Cl]Cl and [Pt(PNCHP-κ 3 P, N, P)(PPh 3)](BF 4) 2, and the five-coordinate complexes, [Pt(PNCHP-κ 3 P, N, P)L](BF 4) 2 (L=1,10-phenanthroline and 2,2 ′:6 ′,2″-terpyridine), have been determined.

A General and Mild Ullmann-Type Synthesis of Diaryl Ethers

[reaction: see text] An efficient method for the synthesis of diaryl ethers under particularly mild conditions is described. Inexpensive ligands were found to greatly accelerate the Ullmann-type coupling of aryl bromides or iodides with phenols. A series of diaryl ethers were obtained with excellent yields in acetonitrile in the presence of Cs(2)CO(3) and catalytic copper(I) oxide. The reaction tolerates substrates with unfavorable substitution patterns, such as sterically hindered coupling partners or electron-rich aryl halides.

Heteroatom-Substituted Carbene Complexes of High-Valent Tungsten: Tp‘W(O)X(C(R)OSiR3) Derivatives

Reaction of Tp‘W(O)(I)(CO) (1; Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) with MeLi followed by trapping of the resultant anion by ClSiPh2Me leads to the formation of a single isomer of the tungsten(VI) heteroatom-substituted carbene complex Tp‘W(O)(I)(C(Me)OSiPh2Me) (5a). The connectivity of complex 5a was confirmed by X-ray crystallography and spectral data. The acyl intermediate in the reaction, [Tp‘W(O)(I)(C(O)Me)][Li] (6), was observed by spectroscopic techniques. Trapping of the acyl intermediate 6 with H+ yields the neutral hydroxy carbene complex Tp‘W(O)(I)(C(Me)OH) (5c). Reaction of complex 1 with PhLi generates the anionic phenyl−acyl complex [Tp‘W(O)(I)(C(O)Ph)][Li] (8), which may be trapped with ClSiPh2Me, yielding the phenyl carbene complex Tp‘W(O)(I)(C(Ph)OSiPh2Me) (7). Carbene complex 5a reacts with AgSO3CF3 to form silver iodide and a coordinated triflate complex, Tp‘W(O)(OSO2CF3)(C(Me)OSiPh2Me) (9). In contrast to the acyl product formed with MeLi and 1, combining LiCuMe2 with 1 leads to the replacement of iodide by a methyl group to form Tp‘W(O)(Me)(CO) (2). Protonation of this methyl tungsten complex (2) in CH2Cl2 in the presence of acetonitrile yields methane and the cationic nitrile adduct [Tp‘W(O)(CO)(NCMe)]+ (3), while protonation of 2 in neat acetonitrile produces a cationic hydroxy carbene complex, [Tp‘W(O)(NCMe)(C(Me)OH)]+ (4).

Oxorhenium(V) complexes with the non-sulfur-containing amino acid histidine.

Equivalent amounts of ReOX(3)(OPPh(3))(Me(2)S) (where X = Cl, Br) and L-histidine (L-hisH) in acetonitrile yield ReOX(2)(L-his), in which the amino acid monoanion is N,N,O-tridentate. X-ray diffraction work on both compounds shows that the three donors occupy a face in a distorted octahedron and the carboxylate oxygen is coordinated trans to the Re=O bond. The 2:1 complex [ReO(L-his)(2)]I is obtained by reacting 2 equiv of L-histidine with ReO(2)I(PPh(3))(2) in methanol in the presence of NaOCH(3). (1)H NMR spectroscopy indicates that these complexes contain one N,N,O-tridentate histidine anion coordinated as above and one N,N-bidentate histidine anion, whose carboxylate group is free. By refluxing ReOX(2)(L-his) in methanol, the carboxylic groups esterify and two octahedral units condense into an oxo-bridged dinuclear complex [ReOX(2)(L-hisMe)](2)O containing N,N-bidentate histidine methyl ester. The O=Re-O-Re=O backbone is approximately linear, and the two ReOX(2)(L-hisMe) units are related by a 2-fold axis through the central oxygen. Crystals of [ReOBr(2)(L-hisMe)](2)O consist of an ordered phase containing two of the possible diastereoisomers in a 1:1 ratio. (1)H NMR spectra of these crystals include two sets of signals, consistent with the presence of two isomers with C(2) symmetry, and the spectra of the nonrecrystallized material confirm that these are the only two isomers formed.

A p-tert-butylcalix[6]arene bearing phosphinoyl pendant arms for the complexation and sensitisation of lanthanide ions

The new lower rim functionalised macrocycle 5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41,42-hexakis(dimethylphosphinoylmethoxy)calix[6]arene (B6bL6) has been synthesised. Temperature dependent 1H and 31P NMR studies indicate a mixture of conformers with a time-averaged C6v symmetry at 405 K in dmso-d6; ΔG≠ values for conformational interconversion processes are equal to 68(1) and 75(2) kJ mol−1 and reveal a semi-flexible macrocycle with alternate in-out cone conformation, a fact confirmed by molecular mechanics and dynamics calculations. B6bL6 crystallises as a dimer where the two calixarenes are linked through hydrogen bonding and surrounded by water and toluene molecules in the lattice. UV-Vis spectrophotometric titration of B6bL6 with La(III) in acetonitrile yields stability constants logβ1 = 9.8 and logβ2 = 19.6 for the 1 ∶ 1 and 1 ∶ 2 (Ln ∶ B6bL6) species, respectively. The corresponding complexes with La, Eu, Gd and Tb have been isolated and characterised. Lifetime determinations of the Eu(III) and Tb(III) complexes in acetonitrile solution are consistent with no or little interaction of water molecules in the inner co-ordination sphere. The new ligand sensitises reasonably well the luminescence of the Tb(III) (Qabs = 4.8% , τf = 2.1 ms, 1 ∶ 1 complex) and Eu(III) (Qabs = 2.5%, τ = 2.0 ms, 1 ∶ 2 complex) ions.

Synthesis and Characterization of the Silver Maleonitrilediselenolates and Silver Maleonitriledithiolates [K([2.2.2]-cryptand)]4[Ag4(Se2C2(CN)2)4], [Na([2.2.2]-cryptand)]4[Ag4(S2C2(CN)2)4]·0.33MeCN, [NBu4]4[Ag4(S2C2(CN)2)4], [K([2.2.2]-cryptand)]3[Ag(Se2C2(CN)2)2]·2MeCN, and [Na([2.2.2]-cryptand)]3[Ag(S2C2(CN)2)2

Reaction of AgBF(4), KNH(2), K(2)Se, Se, and [2.2.2]-cryptand in acetonitrile yields [K([2.2.2]-cryptand)](4)[Ag(4)(Se(2)C(2)(CN)(2))(4)] (1). In the unit cell of 1 there are four [K([2.2.2]-cryptand)](+) units and a tetrahedral Ag(4) anionic core coordinated in mu(1)-Se, mu(2)-Se fashion by each of four mns ligands (mns = maleonitrilediselenolate, [Se(2)C(2)(CN)(2)](2)(-)). Reaction of AgNO(3), Na(2)(mnt) (mnt = maleonitriledithiolate, [S(2)C(2)(CN)(2)](2)(-)), and [2.2.2]-cryptand in acetonitrile yields [Na([2.2.2]-cryptand)](4)[Ag(4)(mnt)(4)].0.33MeCN (2). The Ag(4) anion of 2 is analogous to that in 1. Reaction of AgNO(3), Na(2)(mnt), and [NBu(4)]Br in acetonitrile yields [NBu(4)](4)[Ag(4)(mnt)(4)] (3). The anion of 3 also comprises an Ag(4) core coordinated by four mnt ligands, but the Ag(4) core is diamond-shaped rather than tetrahedral. Reaction of [K([2.2.2]-cryptand)](3)[Ag(mns)(Se(6))] with KNH(2) and [2.2.2]-cryptand in acetonitrile yields [K([2.2.2]-cryptand)](3)[Ag(mns)(2)].2MeCN (4). The anion of 4 comprises an Ag center coordinated by two mns ligands in a tetrahedral arrangement. Reaction of AgNO(3), 2 equiv of Na(2)(mnt), and [2.2.2]-cryptand in acetonitrile yields [Na([2.2.2]-cryptand)](3)[Ag(mnt)(2)] (5). The anion of 5 is analogous to that of 4. Electronic absorption and infrared spectra of each complex show behavior characteristic of metal-maleonitriledichalcogenates. Crystal data (153 K): 1, P2/n, Z = 2, a = 18.362(2) A, b = 16.500(1) A, c = 19.673(2) A, beta = 94.67(1) degrees, V = 5941(1) A(3); 2, P4, Z = 4, a= 27.039(4) A, c = 15.358(3) A, V = 11229(3) A(3); 3, P2(1)/c, Z = 6, a = 15.689(3) A, b = 51.924(11) A, c = 17.393(4) A, beta = 93.51(1) degrees, V = 14142(5) A(3); 4, P2(1)/c, Z = 4, a = 13.997(1) A, b = 21.866(2) A, c = 28.281(2) A, beta = 97.72(1) degrees, V = 8578(1) A(3); 5, P2/n, Z = 2, a = 11.547(2) A, b = 11.766(2) A, c = 27.774(6) A, beta = 91.85(3) degrees, V = 3772(1) A(3).

Synthesis and Characterization of Derivatives of a Hydroxymethyl Ruthenium Complex

Reaction of cis-Ru(bpy)2(CO)CH2OH+PF6- (1, bpy = 2,2‘-bipyridine) with acetic anhydride yields the corresponding acetoxymethyl derivative 2. However, reaction of 1 with a large excess of acetic acid in acetonitrile yields compound 3, containing an acetamidomethyl ligand instead of the acetoxymethyl group. Compounds 2 and 3 have been characterized by X-ray crystallography; in the crystalline state, 3 exists as a binuclear compound held together by hydrogen bonds to a single water molecule through the acetyl carbonyl groups.

New linear tricobalt complex of di(2-pyridyl)amide (dpa), [Co3(dpa)4(CH3CN)2][PF6]2.

Reaction of the linear tricobalt compound Co3(dpa)4Cl2 (1) (dpa = di(2-pyridyl)amide) with silver hexafluorophosphate in acetonitrile yields [Co3(dpa)4(CH3CN)2][PF6]2 (2). Two crystalline forms are obtained from the same solution, namely, a monoclinic (P2(1)) form 2xCH3CNx2Et2O and a triclinic (P1) form, 2x3CH3CN. The tricobalt units in both crystals are essentially symmetrical, though this is not required by crystal symmetry, with Co-Co distances in the range 2298-2304 A. Each of the two terminal Co atoms is coordinated to an acetonitrile molecule with Co-N distances in the range 2068-2111 A at 213 K. The spiral arrangement of ligands gives an overall idealized D4 point group symmetry for the cation [Co3(dpa)4(CH3CN)2]2+ . Chiral crystals of both delta and lambda configurations in the P2(1) form have been isolated. The absolute configurations were determined by X-ray crystallography and their mirror-image circular dichroism spectra measured. The D4 symmetry of the cation appears to be preserved in solution as judged by the presence of only five proton resonance signals in the 1H NMR spectrum. Magnetic susceptibility measurements in the solid state indicates that 2 has a doublet ground state and exhibits an increase of the effective moment at high temperature (approximately 160 K) due to a spin crossover process.