2a 2f Research Articles

Novel heterocyclic poly(arylene ether ketone)s: Synthesis and polymerization of 4‐(4′‐hydroxyaryl)(2H)phthalazin‐1‐ones with methyl groups

AbstractBased on green chemistry, a simple and efficient direct synthesis of 4‐(4′‐hydroxyaryl)(2H)phthalazin‐1‐ones (2a–2f) was developed in a two‐step reaction, in which the Friedel–Crafts acylation reaction of six phenols with phthalic anhydride was initially carried out and then followed by cyclization with hydrazine hydrate in good to excellent yields with high regioselectivity. A number of novel heterocyclic poly(arylene ether ketone)s were prepared conveniently from several unsymmetrical, twist, and noncoplanar phthalazinone‐containing monomers (2a–2f) and an activated difluoro monomer via a NC coupling reaction. It was very interesting that the obtained monomers and polymers exhibited diverse properties with the variation of the number and location of the substituted methyl groups. All these polymers had a high molecular weight with Mn and ηinh in the range of 44,960–169,000 Da and 0.38–0.79 dL/g, respectively. Actually, the obtained polymers displayed excellent thermal properties with Tg's ranging from 222 to 248 °C and 5% weight loss temperatures in nitrogen higher than 430 °C. Moreover, these polymers were readily soluble in common organic solvents, such as N‐methyl‐2‐pyrrolidone, chloroform, pyridine, and m‐cresol, and could be cast into flexible and colorless or nearly colorless films by spin‐coating or casting processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1525–1535, 2007

Structural and theoretical investigation of 2-iminoimidazolines ? carbene analogues of iminophosphoranes

The preparation of 2-iminoimidazolines - has been accomplished by the Staudinger reaction of the carbenes 1,3-di-tert-butylimidazolin-2-ylidene (), 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene (), 1,3-diisopropylimidazolin-2-ylidene (), 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (), 1,3-bis(2,6-diisopropylphenylimidazolin-2-ylidene () and 1,3,4,5-tetramethylimidazolin-2-ylidene () with trimethylsilyl azide (Me3SiN3) followed by desilylation of the resulting 2-trimethylsilyliminoimidazolines -. The X-ray crystal structures of and have been established, revealing C1-N1-Si1 angles that are more obtuse than the corresponding P-N-Si angles observed in related trimethylsilyl iminophosphoranes. Together with , the disilylated side product 1,3-diisopropyl-2-(trimethylsilylimino)-4-trimethylsilylimidazoline () has been isolated and structurally characterized. Cleavage of the N-Si bonds in and formation of is easily achieved by stirring in methanol. The molecular structures of the 2-iminoimidazolines are reported, indicating that the structural parameters are best described by non-ylidic resonance structures and that electron delocalization within the imidazole heterocycle does not play a crucial role in these imine systems. Compound forms a head-to-head dimer in the solid state via weak intermolecular N-H...N contacts, which have additionally been characterized by means of compliance constants. To further analyze the electronic structure of these imines in comparison to related guanidine ligands, the proton affinities (PAs) of the model compounds 2-imino-1,3-dimethylimidazoline (), 2-imino-1,3-dimethylimidazolidine () and tetramethylguanidine () have been calculated by means of density functional theory. Finally, the charge distribution in - and the relative contribution of relevant resonance structures have been determined using natural bond orbitals (NBO) and natural resonance theory (NRT).

Synthesis of some new 1-aryl-4-formyl-3-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)pyrazoles using the Vilsmeier–Haack reaction — Isolation of the key intermediate 1-aryl-3-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)pyrazoles

Arylhydrazones of dehydroacetic acid (DHA) underwent Vilsmeier–Haack reaction to generate the corresponding 1-aryl-4-formyl-3-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)pyrazoles (1) with the pyrone moiety of the DHA remaining intact. However, when the reaction was performed using 1 equiv. of the reagent, compounds of 1-aryl-3-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)pyrazoles (2a–2f) were obtained, which underwent smooth conversion to 1-aryl-4-formyl-3-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)pyrazoles (1) on further treatment with another equivalent of the Vilsmeier–Haack reagent. This unreported observation suggests the intermediacy of 1-aryl-3-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)pyrazoles (2) in Vilsmeier–Haack reactions of hydrazones with a pyrone moiety. Several analogous compounds were also prepared using arylhydrazones of DHA.Key words: dehydroacetic acid, pyrazoles, Vilsmeier–Haack reaction, 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one.

Microwave- and ultrasound-assisted semisynthesis of natural methoxylated propiophenones from isomeric mixture of phenylpropenes in minutes

A rapid and practical semisynthesis of natural methoxylated propiophenones (3a–3f) is realized by reacting stereo- and regio-isomeric mixture of phenylpropenes (1a–1f) with a catalytic amount of palladium chloride – sodium formate in formic acid, methanol, and water (2:1:2) into single product phenylpropanes (2a–2f) followed by its oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in wet dioxane, containing a few drops of formic acid. Conventional, ultrasound, and microwave heating were compared through these studies.Key words: focused microwave, ultrasound, phenylpropene, propiophenone, DDQ.

A Rapid and Efficient Microwave‐Assisted Synthesis of Substituted 3‐Phenylpropionic Acids from Benzaldehydes in Minutes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Rapid and Efficient Microwave-Assisted Synthesis of Substituted 3-Phenylpropionic Acids from Benzaldehydes in Minutes

Abstract A convenient, inexpensive, and efficient synthesis of 3-phenylpropionic acids (1a–1f) by reacting benzaldehyde (2a–2f) and malonic acid in acetic acid and piperidine into cinnamic acid (3a–3f) in 77 to 89% followed by its reduction with PdCl2 in the biphase of formic acid and aqueous sodium hydroxide is reported under microwave irradiation which utilizes short reaction time ranging 5 to 7 min to provide 1a–1f in moderate to high yield (69–86%) depending upon methoxy, methylenedioxy, and hydroxy groups present at the phenyl ring.

Diastereoselective formation of a dipalladium(i) complex supported by a bridging tetradentate ligand, and oxidative addition of RS–H across a phosphine-bridged PdI–PdI bondElectronic supplementary information (ESI) available: full synthetic methods and characterisation data for compound 1 and the 2a–2f salts. See http://www.rsc.org/suppdata/cc/b3/b300177f/

The ligand CH2(P(o-C6H4NMe2)2)2 (dmapm) gives access to the first example of a dipalladium(I) complex supported by a tetradentate ligand, Pd2Cl2(mu-N,P,P,N-dmapm), which, unlike the well-known Pd2X2(mu-dppm)2 complexes (X = halide, dppm = bis(diphenylphosphino)methane), reacts with thiols to give addition of RS-H across a phosphine-bridged Pd-Pd bond.

Synthesis and photophysics in organic solvents of mesosubstituted pentamethine and related metal complexes cyanine dyes

The reaction of a ratio of 1 mol of diacetylchloromethane with the heterocyclic nitrogen base afforded N-substituted heheterocyclidinium ylide halide 1a–1f. Reaction of a ratio of 1 mol of 1a–1f with 2 and 3 mol of 2(4)-methylheterocyclic quaternary salts in basic catalyst afforded meso-substituted pentamethine 2a–2f and monomethine meso-substituted pentamethine 3a-3c cyanine dyes respectively. Reaction of equimolar ratios of 6a–6e with equi-(bi)- molar ratios of 2(4)-methylheterocyclic quaternary salts in basic medium afforded asymmetrical (symmetrical) meso-substituted mono-(bis) monomethine metal complex cyanine dyes 7 and 8a–8e. Elemental analyses, IR and 1H NMR spectral data confirmed the structures of newly synthesized compounds. The electronic absorption spectra of these dyes in ethanol and photophysics in different organic solvents are discussed.

Novel optically active poly(amide‐imide)s with tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine moieties by microwave‐assisted polycondensation

AbstractRapid and highly efficient synthesis of novel poly(amide‐imide)s (PAIs) were achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4′‐carbonyl‐bis(phthaloyl‐L‐alanine) diacid chloride [N,N′‐(4,4′‐carbonyldiphthaloyl)] bisalanine diacid chloride (1) with six different derivatives of tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine compounds (2a–2f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly and was almost completed within 10 min, giving a series of PAIs with inherent viscosities of about 0.25–0.45 dL/g. The resulting PAIs were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (ηinh), solubility test, and specific rotation. Thermal properties of the PAIs were investigated using thermogravimetric analysis. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2416–2421, 2001

Effect of phenyl substitution on bonding in η3-benzyl complexes of platinum

Reaction of the platinum(0) styrene complexes [Pt(η2-CH2CHC6H4X){But2P(CH2)3PBut2}]1a–1f(X = Br-3, Br-4, Me-4, F-4, F-3 or MeO-4) with HBF4 in diethyl ether afforded the η3-methylbenzyl complexes [Pt(η3-MeCHC6H4X){But2P(CH2)3PBut2}][BF4]2a–2f. The effect of phenyl substitution on the asymmetry of the η3-methylbenzyl interaction was measured by 31P-{1H} NMR spectroscopy and it was found that, in general, the more electron releasing the substituent, X, the more asymmetric is the bonding. Complexes 2a–2f lose styrene reversibly to form the hydride-bridged dinuclear platinum complex [Pt2(µ-H)2{But2P(CH2)3PBut2}2][BF4]2. Displacement of styrenes from 2a–2f by ethene and bicyclo[2.2.1]hept-2-ene affords known complexes stabilized by a three-centre, two-electron (agostic) bond.

Vinylstannanes: synthesis and characterization

Primary, secondary and tertiary vinylstannanes 2a–2f are synthesized by reduction of the corresponding chloro(vinyl)stannanes. They are characterized by their spectral data (IR, NMR ( 119Sn, 13C, 1H) spectroscopy and mass spectrometry. The 119Sn chemical shifts and 1 J SnH and 1 J SnC of vinylstannanes are compared with the data reported for the corresponding alkyl- and aryl-stannanes. Compounds 2 decompose slowly at room temperature in benzene ( τ 1 2 1–3 days). The formation of divinylchlorostannane and the use of trivinylstannane as a reducing agent are also reported.

Cyclometallation of azine phosphines of type Z,E-PPh2CH2C(But)N–NCHR (R = an aromatic or heterocyclic group) involving X–Y (X = C, N or O; Y = H, I or Br) bond fission by platinum(II)

The phosphino hydrazone Z-PPh2CH2C(But)NNH21 is shown to be a convenient ‘reagent’ for converting aryl or heterocyclic aldehydes into azines which can then be cycloplatinated readily with C–H, C–I, C–Br, N–H or O–H bond fission. Condensation of 1 with benzaldehyde derivatives (RCHO) gave mixed azines of type Z,E-PPh2CH2C(But)N–NCHR [R = Ph 2a, C6H2(OMe)3-3,4,5 2b, C6H4NO2-4 2c, C6H4I-2 2d, C6H4Br-2 2e, C6H4Cl-2 2f or C6H2(OH-2)(OMe)2-4,6 2g]. The azines 2a–2f reacted with [PtMe2(cod)](cod = cycloocta-1,5-diene) at 20 °C to give dimethylplatinum(II) complexes [[graphic omitted]CHR}]3a–3f respectively, containing six-membered chelate rings. Treatment of 2g with [PtMe2(cod)] effected O–H bond fission to give the O-cyclometallated methylplatinum(II) complex [[graphic omitted](OMe)2-4,6]}]4. When the dimethylplatinum(II) complex 3a was heated in toluene at 100 °C, it underwent C–H bond fission with elimination of CH4 to give the cyclometallated methylplatinum(II) complex [[graphic omitted]C6H4)}]5a. Similarly, 3b and 3c were converted into the corresponding cyclometallated methylplatinum(II) complexes 5b and 5c, respectively. The square-planar dimethylplatinum(II) complex 3d in benzene at 20 °C underwent oxidative addition of the C–I bond to give the cyclometallated iododimethylplatinum(IV) complex mer,cis-[[graphic omitted]H4)}]6a. When the bromo-mixed azine complex 3e was heated in benzene at 75 °C for 16 h the cyclometallated bromodimethylplatinum(IV) complex mer,cis-[[graphic omitted]H4)}]6b formed. In contrast the chloro-mixed azine complex 3f underwent the C–H bond fission and not C–Cl bond fission to give the cyclometallated square-planar methylplatinum(II) complex [[graphic omitted]H3Cl-6)}]5d. The methylplatinum(II) complexes 5a and 5d oxidatively added Mel to give the mer,cis-iododimethylplatinum(IV) complexes 6a and 6c, respectely. Treatment of 1 with 2-carbaldehydes of pyrrole, thiophene or furan gave the corresponding phosphines 7a–7c, which with [PtMe2(cod)] at 20 °C gave the dimethylplatinum(II) complexes 8a–8c, respectively. When 8a, derived from the pyrrole azine phosphine, was heated at 50 °C for 10 min, the N-cyclometallated methylplatinum(II) complex [[graphic omitted])}]9 and methane were formed via a N–H bond fission. When the dimethylplatinum(II) complexes 8b or 8c, derived from the thiophene or furan azine phosphines, were heated at 100 °C in toluene they underwent C–H bond fission to give the cyclometallated methylplatinum(II) complexes [[graphic omitted]H2X)}](X = S 10a or O 10b), which oxidatively added Mel to give the iododimethylplatinum(IV) complexes mer,cis-[[graphic omitted]H2X)}](X = S 11a or O 11b), respectively. Proton, 31P-{1H} and some 13C-{1H} NMR data have been obtained.

An AM1 calculational study of the Diels–Alder addition of maleic anhydride to C5-substituted pentamethylcyclopentadienes and 2,5-dimethylthiophene oxide. An attempt to ascertain the factors controlling the π-facial selectivities and relative reactivities

The Diels–Alder reactions of maleic anhydride (1) with a group of C5-substituted cyclopentadienes and 2,5-dimethylthiophene oxide (5) have been studied with the semi-empirical method AM1. We find that the facial selectivities and relative reactivities found experimentally for six dienes (2a–2f) are accurately reproduced at this level of theory. The results of the calculational study provide no concrete support for the proposal that σ–σ* hyperconjugation in the transition state – an interaction between a σ bond at C5 of the cyclopentadiene and the incipient σ bonds anti to it (the Cieplak effect) – is the major source of the syn facial selectivity observed for 2a–2d. In addition, the relative reactivities and facial selectivities are predicted for a number of cyclopentadienes which will be synthesized and studied experimentally.

Diastereoface differentiation in addition of lithium enolates to chiral α,β-epoxyaldehydes

The aldolisation reaction of lithium ester enolates with chiral α,β-epoxyaldehydes 2a–2f has been investigated. The reaction proceeds with diastereofacial preference in favour of the anti isomer ( anti:syn ≈ 4:1) and can be greatly enhanced in the case of cis α,β-epoxy-aldehydes 2a–2c by a synergic effect of temperature and enolate excess ( anti:syn 13:1). The Felkin-Ahn model can explain the results obtained on asymmetric induction.

Monomeric and dimeric acyloxydialkylboranes

The carboxylic acids RCO2H [R = Buta, Et b, 3,4,5-(MeO)3C6H2c, 4-MeOC6H4d, Ph e, 2,4,6-Me3C6H2f, 2,6-Cl2C6H3g, or 3,5-(CF3)2C6H3h] were treated with triethylborane or with bis(9-borabicyclo[3.3.1]nonane) to give the acyloxydiethylboranes 1a–1h and the 9-acyloxy-9-borabicyclo[3.3.1]nonanes)2a–2h, respectively. Compounds 1a–1h are largely unassociated in non-polar solvents (11B NMR, IR spectroscopy). As pure liquids, or in the solid state, they form equilibrium mixtures of monomeric and associated (dimeric) molecules (IR spectroscopy). Compounds 2a–2f are completely associated as pure liquids and in the solid state, but only weakly associated in non-polar solvents. Based on the crystal structure of dimeric 2e, it is proposed that, when associated, derivatives of both 1 and 2 form cyclic dimers.

Computational and ultraviolet photoelectron spectroscopic studies of 5-substituted cyclopentadienes. Evidence that n–π orbital mixing in the HOMO is not the source of the syn π-facial selectivity in Diels–Alder reactions

A series of C5 monomethyl (1a–1f) and pentamethylcyclopentadienes (2a–2f) bearing stereogenic C5 heteroatom substituents (-NH2, -OH, -OCH3, and -SCH3) have been studied computationally (abinitio and AM1) and with ultraviolet photoelectron (pe) spectroscopy. In the case of compounds 1d–1f and 2d–2f, the conformations 3 and 4 of Cs symmetry with the lone paris anti to the cyclopentadiene ring are computed to be the most stable geometries. On the other hand, the twisted-anti conformers 5a and 5b are the most stable geometries of 1c and 2c. Analysis of the computed MO eigenvalues (orbital energies), MO eigenvectors (orbital coefficients), and the pe spectra of cyclopentadienes 2a–2f established that n–π orbital mixing is not important in the HOMO's of 1c–1d or 2c–2d. That the ionization energy of the HOMO is found to be virtually independent of the substituent at C5 in the series 2a–2f, provides support for the computational results. Because 2c–2d undergo Diels–Alder reactions selectively, syn to the heteroatom substituent, n–π orbital mixing in the HOMO cannot be the source of the π-facial selectivity observed for these compounds.

Synthese von Tricarbonyl-η 5-cyclohexadienyl-wolframat und Tricarbonyl-η 5-cyclohexadienyl-methyl-wolfram

η 6-Arene-tricarbonyl-tungsten (arene = benzene ( 1a), toluene ( 1b), m-xylene ( 1C), P-xylene ( 1D), o-xylene ( 1E), mesitylene ( 1F)) yield with potassium-tri-sec-butylboranate correspondingly methyl-substituted tricarbonyl-η 5-cyclohexadienyl-tungstates ( 2A–2F). Similarly 1A reacts with methyllithium to tricarbonyl-η 5- anti-6-methylcyclohexadienyl-tungstate ( 4A). In THF 2A–2F and 4A are converted by methyliodide to tricarbonyl-μ 5-cyclohexadienyl-tungsten ( 3A–3F) and tricarbonyl-η 5- anti-6-methylcyclophexadienyl-methyl-tungsten ( 5A). The complexes were characterized by C, H elemental analyses and by IR and 1H-NMR spectroscopy.

A facile synthesis of 1-halo- and 1-organoxygermatranes

Interaction of the readily available 1-trimethylsilogermatranes ( 1a, 1b) with various halogenating reagents (Me 3SiBr, Me 3SiI, HF and SOCl 2) has given the 1-halogermatranes ( 2a–2f). The 1-halogermatranes ( 2a–2b) have been converted into the corresponding 1-organoxygermatranes by treatment with trialkylalkoxystannanes ( 3a–3f). The corresponding 1-organoxygermatranes ( 4d, 4e, 4f) were made by interaction of 1-hydroxygermatrane monohydrate with the corresponding hydroxy derivatives).

ChemInform Abstract: Kinetic Study on the Reaction of p‐Nitrophenyl Acetate with 6‐Substituted 2,4‐Diamino‐1,3,5‐triazines

The reactions of p-nitrophenyl acetate (1) with six 6-substituted 2,4-diamino-1,3,5-triazines, (2a–2f), were kinetically investigated in aqueous DMSO or in water at 30 °C. It was found that the reaction rate R could be expressed according to the equation R=(k0+kN[2])[1], and that Bronsted-type plots for the kN-reaction give a straight line with a slope (β) of 1.05. The solvent deuterium isotope effect was not observed in this reaction [kN(H)⁄kN(D)=1.0–1.15]. Furthermore, the isolated reaction product was 2-acetylamino-4-amino-6-methyl-1,3,5-triazine (4c), which was formed by a nucleophilic attack of 2c to 1. From these results, the mechanism for this nucleophilic reaction is discussed.

Kinetic Study on the Reaction of p-Nitrophenyl Acetate with 6-Substituted 2,4-Diamino-1,3,5-triazines

Abstract The reactions of p-nitrophenyl acetate (1) with six 6-substituted 2,4-diamino-1,3,5-triazines, (2a–2f), were kinetically investigated in aqueous DMSO or in water at 30 °C. It was found that the reaction rate R could be expressed according to the equation R=(k0+kN[2])[1], and that Brönsted-type plots for the kN-reaction give a straight line with a slope (β) of 1.05. The solvent deuterium isotope effect was not observed in this reaction [kN(H)⁄kN(D)=1.0–1.15]. Furthermore, the isolated reaction product was 2-acetylamino-4-amino-6-methyl-1,3,5-triazine (4c), which was formed by a nucleophilic attack of 2c to 1. From these results, the mechanism for this nucleophilic reaction is discussed.