Synthesis and characterization of photosensitive polyimides from methylthiomethyl-substituted 4,4′-diaminodiphenylmethanes and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride

A series of novel polyimides are synthesized by the reaction of 3,3′,4,4′-benzophenonete-tracarboxylic dianhydride (BTDA) with four methylthiomethyl-substituted aromatic diamines: 3-methylthiomethyl-4,4′-diaminodiphenylmethane ( I ), 3,3′-dimethylthiomethyl-4,4′-diaminodiphenylmethane ( II ), 3,3′,5-trimethylthiomethyl-4,4′-diaminodiphenylmethane ( III ), and 3,3′,5,5′-tetramethylthiomethyl-4,4′-diaminodiphenylmethane ( IV ) in refluxing m-cresol. The polyimide of diamine I and BTDA carrying only one pendant methylthiomethyl group in a repeating unit is readily soluble in m-cresol, chloroform, and polar aprotic solvents. Increasing the number of the pendant group results in higher solubility. These fully imidized polyimides are also intrinsically photosensitive. The fraction of photoreactive benzophenone sites that relates to the rate and degree of completion of photocrosslinking reaction increases systematically with the increase of the pendant group content. As the average number of the pendant group in a repeating unit reaches 3, 63% of benzophenone sites are found to be photoreactive. These methylthiomethyl-substituted polyimides possess moderate tensile strength which falls in the range of 67–81 MPa. As a result of the increase of methylthiomethyl content, this type of polyimide reveals higher glass transition temperature but lower thermal stability due to the considerable dimension of the pendant group and the ready cleavage nature of the C? S bond. © 1993 John Wiley & Sons, Inc.     

Mass spectral fragmentation pattern of 4,4′-bipyridines. Part II. 4,4′-oxybispyridine and 4,4′-thiobispyridine

The mass spectra of 4,4′-oxybispyridine and 4,4′-thiobispyridine are reported. In the former the base peak is due to the molecular ion and the fragmentation routes involve loss of H, CO, HCN, C₂H₂N and C_sHO from the molecular ion as well as rupture of the central bonds. In the latter the base peak is also due to the molecular ion and the fragmentation routes involve loss of H, CS, S, HCN and C₂HS as well as central bond rupture.     

Enolethers. XXI. Synthesis of 5,5′-disubstituted 4,4′-bipyrimidines

1,6-Dialkoxy-3,4-diones 3 are easily accessible by acylation of enol ethers 1 with oxalyl chloride and subsequent elimination of hydrogen chloride using triethylamine. The open-chain 2,5-dimethyl derivative 3b is converted with amidines 4a-c and S-methylisothiourea (4d) , respectively, to give 2,2′-disubstituted 5,5′-dimethyl-4,4′-bipyrimidines 5a-d . The dihydrofuran and dihydropyran derivatives 3c and 3d , however, react with benzamidine (4c) in dimethylformamide only in the presence of calcium hydride as condensation agent yielding 5,5′-bis(2-hydroxyethyl)- and 5,5′-bis(3-hydroxypropyl)-2,2′-diphenyl-4,4′-bipyrimidine 6a and b.     

Synthesis and properties of polyimides from 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride

4,4′-Binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride was synthesized from 4-chloro-1,8-naphthalic anhydride and polymerized with aromatic and pliphatic diamines in m-cresol or N-methyl-2-pyrrolidinone (NMP). The polyimides, except for two derived from p-phenylenediamine and hydrazine, are soluble in 1,1,2,2-tetrachloroethane and NMP. Their intrinsic viscosities ranged from 0.36 to 2.20 dL/g. The polymers showed excellent thermal and thermooxidative stabilities and displayed weak glass transition temperatures. Young's moduli of some polymer films were in the range of 2.5 and 5.4 GPa at 30°C. The aliphatic polyimides exhibited a stronger fluorescence than the aromatic polyimides. © 1995 John Wiley & Sons, Inc.     

Synthesis of Certain 5-Substituted 2′-Deoxytubercidin Derivatives

The synthesis of the 7-deaza-2′-deoxy-adenine derivatives 7b–3 with chloro, bromo, or methyl substituents at C(5) is described. Glycosylation of the 5-substituted 4-chloropyrrolo[2,3-d]pyrimidines 4b–d with 2-deoxy-3,5-di-O-(4-toluoyl)-α-D -erythro-pentofuranosyl chloride ( 3 ) gave the β-D -nucleosides 5b–d , exclusively. They were deblocked (→ 6b–d ) and converted into the tubercidin derivatives 7b–d .     

Mass spectra of some tetrasubstituted 4,4′-biisoxazoles and 4,4′-methylendiisoxazoles

The behaviour of some tetrasubstituted 4,4′-biisoxazoles and 4,4′-methylendiisoxazoles under electron impact has been investigated by means of high and low resolution mass spectrometry. The determination of metastable transitions and accurate masses of important fragment ions has led to the construction of fragmentation schemes. Specific skeletal rearrangement processes are discussed and it is proposed that they proceed through azirine and oxazole intermediates.     

Synthesis of 6-Substituted 1-Deazapurine 2′-Deoxyribonucleosides

The synthesis of 6-substituted 1-deazapurine 2′-deoxyribonucleosides is described. Glycosylation of the 1-deazapurine (imidazo[4,5-b]pyridine) anions with the α-D -halogenose 5 gives stereoselectively N⁷- and N⁹- regioisomers. ¹H-NMR NOE and ¹³C-NMR spectroscopy are used for unambiguous assignment of isomers, and ¹⁵N-NMR chemical shifts are correlated with σ_para Hammett constants and point charges.     

The First Total Synthesis of 4,4′-Biisofraxidin

Ｉｎｔｒｏｄｕｃｔｉｏｎ　　 4 ,4′ Ｂｉｉｓｏｆｒａｘｉｄｉｎ (1) ,ａｎｅｗｂｉｓｃｏｕｍａｒｉｎ ,1ｗａｓｉｓｏｌａｔｅｄｂｙＷａｎｃｈａｉＤｅ Ｅｋｎａｍｋｕｌａｎｄｈｉｓｃｏ ｗｏｒｋｅｒｓｆｒｏｍｔｈｅｒｏｏｔｃｕｌｔｕｒｅｓｏｆｉｍｐａｔｉｅｎｓｂａｌｓａｍｉｎａＬ . (Ｂａｌ ｓａｍｉｎａｃｅａｅ) ,ｗｈｉｃｈｈａｓｌｏｎｇｂｅｅｎｕｓｅｄｉｎＴｈａｉｌａｎｄａｓａｔｒａｄｉｔｉｏｎａｌｆｏｌｋｍｅｄｉｃｉｎｅ .ＴｈｅｌｅａｖｅｓｏｆＢａｌｓａｍｉｎａｃｅａｅａｒｅｕｓｕａｌｌｙｕｓｅｄｆ…     

Synthesis of difurazanyl ethers from 4,4′‐dinitroazoxyfurazan

Nonselective attacks at the carbon bonded to a nitro group and carbon bonded to the N(O) atom of the azoxy group were observed in the reactions of 4,4′‐dinitroazoxyfurazan with bases and nucleophiles. A mechanism is presented to account for both of the pathways to products. A series of new difurazanyl ether derivatives was synthesized. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:48–56, 2000     

Synthesis and characterization of poly(arylene ether)s derived from 4,4′‐bishydroxybiphenyl and 4,4′‐bishydroxyterphenyl

A series of poly(arylene ether)s were successfully prepared by aromatic, nucleophilic substitution reactions with various perfluoroalkyl‐activated bisfluoromonomers with 4,4′‐bishydroxybiphenyl and 4,4′‐bishydroxyterphenyl. 4,4′‐Bishydroxyterphenyl was synthesized through the Grignard coupling reaction of magnesium salt of 4‐bromoanisole with dibromobenzene followed by demethylation with pyridine–hydrochloride. The products obtained by the displacement of fluorine atoms exhibited good inherent viscosity, up to 0.77 dL/g, and number‐average molecular weights up to 69,300. These poly(arylene ether)s showed very good thermal stability, up to 548 °C for 5% weight loss according to thermogravimetric analysis under synthetic air, and high glass‐transition temperatures, up to 259 °C according to differential scanning calorimetry, depending on the exact repeat unit structure. These polymers were soluble in a wide range of organic solvents, such as N‐methylpyrrolidone, dimethylformamide, tetrahydrofuran, toluene, and CHCl₃, and were insoluble in dimethyl sulfoxide and acetone. Thin films of these poly(arylene ether)s showed good transparency and exhibited tensile strengths up to 132 MPa, moduli up to 3.34 GPa, and elongations at break up to 84%, depending on their exact repeating unit structures. These values are comparable to those of high‐performance thermoplastic materials such as poly(ether ether ketone) (PEEK) and Ultem poly(ether imide) (PEI). These poly(arylene ether)s exhibited low dielectric constants. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 55–69, 2002     

C2-Symmetric 4,4′,5,5′-Tetrahydrobi(oxazoles) and 4,4′,5,5′-Tetrahydro-2,2′-methylenebis[oxazoles] as Chiral Ligands for Enantioselective Catalysis Preliminary Communication

The synthesis of a series of enantiomerically pure, C₂-symmetric 4,4′,5,5′-tetrahydro-2,2′-methylenebis[oxazoles] and 4,4′,5,5′-tetrahydro-2,2′-bi(oxazoles) is reported. Copper complexes with anionic tetrahydromethylenebis[oxazole] ligands are efficient catalysts for the enantioselective cyclopropane formation from olefins and diazo compounds (up to 96% ee in the reaction of styrene with menthyl diazoacetate). Tetrahydrobi(oxazole)iridium(I) complexes were found to catalyze transfer hydrogenations of aryl alkyl ketones with i-PrOH (up to 91% ee). Tetrahydrobi(oxazole)palladium complexes can be used as enantioselective catalysts for allylic nucleophilic substitution (up to 77% ee in the reaction of PhCH?CHCH(OAc)Ph with NaHC(COOMe)₂).     

Dynamic Helicates Self-Assembly from Homo- and Heterotopic Dynamic Covalent Ligand Strands

The understanding and the application of reversible covalent reactions and coordination chemistry together with the proper design of the molecular frameworks, allow to achieve not only well-defined output architectures but also different grades of complex behavior. In this work, the dynamic nature of the helical systems offers an additional level of complexity by combining self-sorting on two levels: 1) the build-up of the ligand strand constituents from their components through dynamic covalent chemistry; 2) the assembly of the helicates from the ligands and the metal cations through dynamic metallo-supramolecular chemistry. The information encoded in the ligands constituent molecule was read differently (and accurately at the same time) by metal cations that varied in the coordination algorithms. It enabled the selective formation of a specific type of helicates from a wide library of helicates formed by the possible combination of subcomponents. Ligands containing dynamic tridentate and/or bidentate binding motifs in the same strand were studied to explore the helicates self-assembly with appropriate metal cations.     

Synthesis and characterization of novel polyaryloxydiphenylsilane derived from 2,2′- dimethyl-biphenyl-4,4′-diol

A novel polyaryloxydiphenylsilane was synthesized successfully by solution polycondensation of 2,2′-dimethyl-biphenyl-4,4′-diol with diphenyldichlorosilane and the catalyst triethylamine in toluene at 80 °C. Polymers with a relatively high inherent viscosity and yield were obtained when the reactions were carried out in aromatic and lipophilic solvents. The novel polyaryloxydiphenylsilane was soluble in chlorinated aliphatic hydrocarbons such as methylene chloride and chloroform as well as in polar solvents such as dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide and also in some common organic solvents such as benzene and toluene. However, it was insoluble in both aliphatic hydrocarbons as well as in alcoholic solvents. The polyaryloxydiphenylsilane began losing weight around 400 °C under a nitrogen atmosphere, and the 10% weight-loss temperature was 473 °C. The glass-transition temperature of the polyaryloxydiphenylsilane was 102 °C. The glass transition could be lowered by the copolymerization technique with 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane as an aromatic diol comonomer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4591–4595, 1999     

3′-Substituted pyrimidines via alkylation-opening of 2,3′-cyclothymidine

Substituted thymidine derivatives are of interest because of their potential antiviral properties. We demonstrate a general strategy for synthesis of 3′-substituted thymidine derivatives, consisting of activation via N-3 alkylation of 2,3′-cyclothymidine followed by nucleophilic opening at the 3′-position. Examples include demonstration of carbon-carbon bond formation at the 3′-position.     

Biselenienyl series. II. Synthesis and resolution of 2,2′-dinitro-3,3′-biselenienyl-4,4′-dicarboxylic acid

2,2′-Dinitro-3,3′-biselenienyl-4,4′-dicarboxylic acid (VI), the first recorded compound of the 3,3′-biselenienyl series, has been prepared and resolved into its optical antipodes by fractional crystallization of its brucine salt. On the basis of the quasi-racemate method of Fredga and the O.R.D. spectra, to the dextrorotatory acid is assigned the R configuration.     

Synthesis of symmetrical 2,2′,4,4′-tetrasubstituted[4,4′-bioxazole]-5,5′(4H,4′H)-diones and their reactions with some nucleophiles

Several symmetrical 2,2′,4,4′-tetrasubstituted[4,4′-bioxazole]-5,5′(4H,4′H)-diones 1a-f were obtained by dehydrodimerization of 5(4H)-oxazolones 2a-f . The configurations of four were established; one by X-ray crystallography rac- 1c , and three rac- 1a , meso- 1a and rac- 1b by ¹H nmr spectroscopy of their derivatives. Upon being heated, the bioxazolones isomerized, presumably by breakage of the 4,4′-carbon? carbon bond to form free radicals followed by their recombination. The results of a crossover experiment were consistent with a radical nature for this isomerization reaction. Treatment of three of the bioxazolones rac- 1a , meso- 1a and rac- 1c with methanol and amine nucleophiles led to ester and amide derivatives 7–11 of α,α'-dehydrodimeric amino acids.     

Thermotropic liquid‐crystalline polyesters of 4,4′‐biphenol and phenyl‐substituted 4,4′‐biphenols with 4,4′‐oxybisbenzoic acid

A series of thermotropic polyesters, derived from 4,4′‐biphenol (BP), 3‐phenyl‐4,4′‐biphenol (MPBP), and 3,3′‐bis(phenyl)‐4,4′‐biphenol (DPBP), 4,4′‐oxybisbenzoic acid (4,4′‐OBBA), and other aromatic dicarboxylic acids as comonomers, were prepared by melt polycondensation and were characterized for their thermotropic liquid‐crystalline (LC) properties with a variety of experimental techniques. The homopolymer of BP with 4,4′‐OBBA and its copolymers with either 50 mol % terephthalic acid or 2,6‐naphthalenedicarboxylic acid had relatively high values of the crystal‐to‐nematic transition (448–460 °C), above which each of them formed a nematic LC phase. In contrast, the homopolymers of MPBP and DPBP had low fusion temperatures and low isotropization temperatures and formed nematic melts above the fusion temperatures. Each of these two polymers also exhibited two glass‐transition temperatures, which were associated with vitrified noncrystalline (amorphous) regions and vitrified LC domains, as obtained directly from melt polycondensation. As expected, they had higher glass‐transition temperatures (176–211 °C) than other LC polyesters and had excellent thermal stability (516–567 °C). The fluorescence properties of the homopolymer of DPBP with 4,4′‐OBBA, which was soluble in common organic solvents such as chloroform and tetrahydrofuran, were also included in this study. For example, it had an absorption spectrum (λ_max = 259 and 292 nm), an excitation spectrum (λ_ex = 258 and 292 nm with monitoring at 350 nm), and an emission spectrum (λ_em = 378 nm with excitation at 330 nm) in chloroform. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 141–155, 2002