PMR study of the reaction of bis(p-aminophenyl)pyrimidines with maleic anhydride in dimethylacetamide

Conclusions An investigation of the reaction of 2,5-bis(p-aminophenyl)pyrimidine with maleic anhydride in N,N-dimethylacetamide showed that the acylation of amines by carboxylic acid anhydrides in amide solvents is characterized by acid autocatalysis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2716–2719, December, 1988.The authors thank V. P. Mamaev and V. P. Borovik for providing samples of the diaminopyrimidines.     

Polyamides from Aromatic BisaminesChloral Derivatives and Terephthaloyl Chloride by Interfacial Polycondensation

Investigations on a new class of polyamides obtained by interfacial polycondensation from amine-chloral derivatives, e.g., 2,2-bis(p-aminophenyl)-1,1,1-trichloromethane or 2,2-bis(p-aminophenyl)-1, 1-dichloroethylene and terephthaloyl chloride, have been carried out. It was found that the interfacial process proceeds in the most advantageous way in acidic medium at 0°C using equivalent volume amounts and equimolar concentrations of methylene chloride and water phases in the presence of a stoichiometric quantity of triethylamine as the hydrogen acceptor.     

2,6-二（对氨基苯）苯并[1,2-d;5,4-d']二噁唑的合成和纯化

1,2,3-三氯苯经过硝化、水解、催化加氢、缩合等四步反应，合成了2,6-二（ 对氨基苯）苯并[1,2-d;5,4-d']二噁唑，总产率为70%。同时，研究了一种有效的? 亟峋?,6-二（对氨基苯）苯并[1,2-d;5,4-d']二噁唑的方法。与其他方法相比， 该法原料便宜易得，产物可作为聚合反应的单体原料。     

Enantioselective hydrogenation of acyclic aromatic N-aryl imines catalyzed by an iridium complex of (S,S)-1,2-bis(tert-butylmethylphosphino)ethane

[reaction: see text] An iridium(I) complex of (S,S)-1,2-bis(tert-butylmethylphosphino)ethane with tetrakis(3,5-bis(trifluoromethyl)phenyl)borate as the counterion catalyzes the hydrogenation of acyclic aromatic N-aryl imines under 1 atm of hydrogen pressure at room temperature to give the corresponding optically active secondary amines with up to 99% ee.     

Enantio- and diastereoselective hydrogenation via dynamic kinetic resolution by a cationic iridium complex in the synthesis of beta-hydroxy-alpha-amino acid esters

Anti-selective asymmetric hydrogenation of alpha-amino-beta-keto esters via dynamic kinetic resolution under low hydrogen pressure has been achieved by an easily-handled cationic iridium complex with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF) as a counterion.     

Rhodium-complex-catalyzed asymmetric hydrogenation: transformation of precatalysts into active species

The use of diolefin-containing rhodium precatalysts leads to induction periods in asymmetric hydrogenation of prochiral olefins. Consequently, the reaction rate increases in the beginning. The induction period is caused by the fact that some of the catalyst is blocked by the diolefin and thus not available for hydrogenation of the prochiral olefin. Therefore, the maximum reaction rate cannot be reached initially. Due to the relatively slow hydrogenation of cyclooctadiene (cod) the share of active catalysts increases at first, and this leads to typical induction periods. The aim of this work is to quantify the hydrogenation of the diolefins cyclooctadiene (cod) and norborna-2,5-diene (nbd) for cationic complexes of the type [Rh(ligand)(diolefin)]BF(4) for the ligands Binap (1,1'-binaphthalene-2,2'-diylbis(phenylphosphine)), Me-Duphos (1,2-bis(2,5-dimethylphospholano)benzene, and Catasium in the solvents methanol, THF, and propylene carbonate. Furthermore, an approach is presented to determine the desired rate constant and the resulting respective pre-hydrogenation time from stoichiometric hydrogenations of the diolefin complexes via UV/Vis spectroscopy. This method is especially useful for very slow diolefin hydrogenations (e.g., cod hydrogenation with the ligands Me-Duphos, Et-Duphos (1,2-bis(2,5-diethylphospholano)benzene), and dppe (1,2-bis(diphenylphosphino)ethane).     

Enantioselective hydrogenation of alkenes and imines by a gold catalyst

A new neutral dimeric gold(I) complex bearing the 1,2-bis[(2R,5R)-2,5-dimethylphospholanebenzene] [(R,R)-Me-Duphos] ligand has been synthesized which catalyzes the asymmetric hydrogenation of alkenes and imines under mild reaction conditions.     

Preparation of optically active peralkyldiphosphines and their use, as the rhodium(I) complex, in the asymmetric catalytic hydrogenation of ketones

Two types of the optically active peralkyldiphosphine, 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(dialkylphosphino)butane (Rdiop 3) and N-(N′-substituted carbamoyl-4-dicyclohexylphosphino-2-dicyclohexylphosphinomethylpyrrolidine (R-Cycapp 8), have been prepared by various synthetic methods. Rhodium(I) complexes of 3 and 8 showed high catalytic activity for hydrogenation of various kinds of prochiral ketones, which were reduced smoothly to the corresponding optically active hydroxy compounds, under hydrogen at atmospheric pressure and ambient temperature. The neutral rhodium(I) complexes (diphosphine-Rh^N) hydrogenated -ketoamides and -ketopantolactone in fairly high optical yields (66–77%ee). In the hydrogenation of N-(-ketoacyl)--amino esters, the Cydiop-Rh^N catalyst showed a marked contrast to the diop-Rh^N system; in the hydrogenation of the methyl ester of N-(phenylglyoxyl)-(S)--phenylalanine, 72%de was attained with little double asymmetric induction by the chiral center in the substrate.     

1,4:3,6-dianhydro-2,5-dideoxy-2,5-bis(diphenylphosphino)-l-iditol. A new chiral ligand for asymmetric hydrogenation with rhodium complexes as catalysts

A new chiral 1,4-diphosphine, 1,4:3,6-dianhydro-2,5-dideoxy-2,5-bis(diphenylphosphino)-l-iditol, has been prepared from d-mannitol. Rhodium complexes of this ligand are asymmetric homogeneous hydrogenation catalysts for dehydroamino acids, giving (S)-amino acids in 21–58% optical yields.     

非螯合型手性双膦/钌催化的不对称氢化反应

对RuCl₃和手性双膦(2S,5S)-2,5-双-(二苯膦)-1,4∶3,6-双脱水-2,5-双去氧-L-艾杜醇(BDPI)催化的不对称氢化反应进行了研究,反应的转化率为100%,光学收率受[双膦]/[RuCl₃]比值的影响较大.在α-乙酰胺基肉桂酸的催化氢化反应中,[双膦]/[RuCl₃]=2.0时e.e.值最大,为68%;对衣糠酸的催化氢化,[双膦]/[RuCl₃]=3时e.e.值最大,为92%.     

2,5-Dimethylfuran Production by Catalytic Hydrogenation of 5-Hydroxymethylfurfural Using Ni Supported on Al2O3-TiO2-ZrO2 Prepared by Sol-Gel Method: The Effect of Hydrogen Donors

5-Hydroxymethylfurfural (5-HMF) has been described as one of the 12 key platform molecules derived from biomass by the US Department of Energy, and its hydrogenation reaction produces versatile liquid biofuels such as 2,5-dimethylfuran (2,5-DMF). Catalytic hydrogenation from 5-HMF to 2,5-DMF was thoroughly studied on the metal nickel catalysts supported on Al₂O₃-TiO₂-ZrO₂ (Ni/ATZ) mixed oxides using isopropanol and formic acid (FA) as hydrogen donors to find the best conditions of the reaction and hydrogen donor. The influence of metal content (wt%), Ni particle size (nm), Nickel Ni⁰, Ni⁰/NiO and NiO species, metal active sites and acid-based sites on the catalyst surface, and the effect of the hydrogen donor (isopropanol and formic acid) were systematically studied. The structural characteristics of the materials were studied using different physicochemical methods, including N₂ physisorption, XRD, Raman, DRS UV-Vis, FT-IR, SEM, FT-IR Py_ad, H₂-TPD, CO₂-TPD, H₂-TPR, TEM and XPS. Second-generation 2,5-DMF biofuel and 5-HMF conversion by-products were analyzed and elucidated using ¹H NMR. It was found that the Ni⁰NiO/ATZ3_WI catalyst synthesized by the impregnation method (WI) generated a good synergistic effect between the species, showing the best catalytic hydrogenation of 5-HMF to 2,5-DMF using formic acid as a hydrogen donor for 24 h of reaction and temperature of 210 °C with 20 bar pressure of Argon (Ar).     

Synthesis of chiral hydroxyl phospholanes from D-mannitol and their use in asymmetric catalytic reactions

Chiral hydroxyl monophosphane 3 [(2S,3S,4S,5S)-3,4-dihydroxy-2, 5-dimethyl-1-phenylphospholane] and bisphospholanes 5a [1,2-bis[(2S, 3S,4S,5S)-3,4-dihydroxy-2,5-dimethylphospholanyl]benzene] and 5b [1, 2-bis[(2S,3S,4S,5S)-2,5-diethyl-3,4-dihydroxyphospholanyl]benzene] were synthesized from readily available D-mannitol in high yields. Strategies for protection and deprotection of OH-groups in the presence of phosphines have been explored. Rate acceleration in the Baylis-Hillman reaction was observed when a hydroxyl phosphine was used as the catalyst. Rhodium complexes with chiral bisphospholanes are highly enantioselective catalysts for the asymmetric hydrogenation of various kinds of functionalized olefins such as dehydroamino acid derivatives, itaconic acid derivatives, and enamides. An interesting feature of the hydroxyl phospholane system is that hydrogenation of some substrates can be carried out in water with >99% ee and 100% conversion (e.g., itaconic acid).     

2,5-Dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene: first member of the hetero-DuPHOS family

[reaction: see text] The 2,5-dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene (UlluPHOS), a new thiophene-based analogue of (R,R)-1,2-bis(phospholano)benzene (Me-DuPHOS), was synthesized, geometrically and electronically characterized, and employed as ligand of Rh and Ru in some standard hydrogenation reactions of prostereogenic functionalized carbon-carbon and carbon-oxygen double bonds. The synthesis of UlluPHOS is much easier than that provided for Me-DuPHOS. UlluPHOS and Me-DuPHOS display very similar geometries, while the electronic availability of the former is higher than that exhibited by the latter. The Rh and Ru complexes of UlluPHOS produced excellent enantiomeric excesses (98.9-99.5%) in the hydrogenation of N-acetyl-alpha-enamino acids and reaction rates higher than those found when employing the analogous complexes of Me-DuPHOS.     

3,3-二{2,2-二[4-(N,N-二取代氨基)苯基]乙烯基}-4,5,6,7-四氯-2-苯并[c]呋喃酮的合成

在对甲苯磺酸存在下，采用1,1-二[4-(N,N-二取代氨基)苯基]乙烯(3)和四氯苯酐在乙酸酐溶液中的缩合反应合成了3,3-二{2,2-二[4-(N,N-二取代氨基)苯基]乙烯基}-4,5,6,7-四氯-2-苯并[c]呋喃酮(4)，产率89～93%。3由4,4'-二(N,N-二取代氨基)二苯甲酮(1)与甲基碘化镁进行Grignard反应的产物经水解再脱水制得，产率85%～88.5%(以1为基准)。     

Diastereo‐ and Enantioselective Hydrogenation of α‐Amino‐β‐Keto Ester Hydrochlorides Catalyzed by an Iridium Complex with MeO‐BIPHEP and NaBArF: Catalytic Cycle and Five‐Membered Chelation Mechanism of Asymmetric Hydrogenation

The development of Ir‐catalyzed asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides is described. This reaction proceeds through a dynamic kinetic resolution to produce anti‐β‐hydroxy‐α‐amino acid esters in a high diastereo‐ and enantioselective manner. Mechanistic studies have revealed that this unique asymmetric hydrogenation proceeds through reduction of the ketone moiety via the five‐membered transition state involving the chelation between the oxygen of the ketone and the nitrogen of the amine function. The relationship studies between the hydrogen pressure and the stereoselectivity have disclosed two mechanisms dependent on hydrogen pressure. Under low hydrogen pressure (<15 atm), the reaction rate proportionally increased with the hydrogen pressure. However, under the high hydrogen conditions, the reaction rate exponentially accelerated along with the increasing hydrogen pressure, which suggests the participation of two or more of hydrogen atoms.     

Protonation and subsequent intramolecular hydrogen bonding as a method to control chain structure and tune luminescence in heteroatomic conjugated polymers

We report the effects of protonation on the structural and spectroscopic properties of 1,4-dimethoxy-2,5-bis(2-pyridyl)benzene (9) and the related AB coploymer poly(2,5-pyridylene-co-1,4-[2,5-bis(2-ethylhexyloxy)]phenylene) (7). X-ray crystallographic analysis of 9, 1,4-dimethoxy-2,5-bis(2-pyridyl)benzene bis(formic acid) complex 10, and 1,4-dimethoxy-2,5-bis(2-pyridinium)benzene bis(tetrafluoroborate salt) (11) establishes that reaction of formic acid with 9 does not form an ionic pyridinium salt in the solid state, rather, the product 10 is a molecular complex with strong hydrogen bonds between each nitrogen atom and the hydroxyl hydrogen in formic acid. In contrast, reaction of 9 with tetrafluoroboric acid leads to the dication salt 11 with significant intramolecular hydrogen bonding (N-H.O-Me) causing planarization of the molecule. The pyridinium and benzene rings in 11 form a dihedral angle of only 3.9 degrees (cf. pyridine-benzene dihedral angles of 35.4 degrees and 31.4 degrees in 9, and 43.8 degrees in 10). Accordingly, there are large red shifts in the optical absorption and emission spectra of 11, compared to 9 and 10. Polymer 7 displays a similar red shift in its absorption and photoluminescence spectra upon treatment with strong acids in neutral solution (e.g. methanesulfonic acid, camphorsulfonic acid, and hydrochloric acid). This is also observed in films of polymer 7 doped with strong acids. Excitation profiles show that emission arises from both protonated and nonprotonated sites in the polymer backbone. The protonation of the pyridine rings in polymer 7, accompanied by intramolecular hydrogen bonding to the oxygen of the adjacent solubilizing alkoxy substituent, provides a novel mechanism for driving the polymer into a near-planar conformation, thereby extending the pi-conjugation, and tuning the absorption and emission profiles. The electroluminescence of a device of configuration ITO/PEDOT/polymer 7/Ca/Al is similarly red-shifted by protonation of the polymer.     

The role of the pyrimidine ring in the main chain of polyamic acids and polyimides

A comparative study of the behavior of polypyromellitamic acids based on 2,5-bis(p-aminophenyl)pyrimidine and 4,4″-diaminoterphenyl in concentrated dimethylacetamide solutions was carried out by the light-scattering method. It was shown that mutual ordering of the scattering elements is much higher for the pyrimidine-containing polyamic acids than for benzenoid polyamic acids. The Flory-Huggins parameters of the polymer-solvent interaction thus determined indicate that the polymer-polymer interactions increase when a pyrimidine ring is introduced into the polyamic acid or polyimide. Hence, the hypothesis postulating that the amide solvent is displaced by the pyrimidine ring during the shear packing of pyrimidine-containing polymers is confirmed.     

Hydrogenolysis of cubane

On catalytic hydrogenation over Pd-C under normal conditions cubane (10) takes up 3 mol of hydrogen in a few hours. Bicyclo[2.2.2] octane (13) is formed as the main product, and tetracyclo[4.2.0.0^2,5.0^3,8]octane (11, secocubane) and tricyclo[4.2.0.0^2,5]octane (12,nortwistbrendane) have been identified as intermediates. The hydrogenolysis of dimethyl 1,4-cubane dicarboxylate, as well as cuneane derivatives, have also been studied. Results are discussed in terms of strain relief calculated by the molecular mechanics method for cubane-like structures.     

纳米多孔钯催化亚胺化合物加氢还原反应研究

本文首次研究了以H2为氢源、纳米多孔钯催化亚胺化合物的加氢还原反应.结果表明:在氢气压力为101.325 kPa,溶剂为无水乙醇,反应温度为30℃,反应时间24 h,催化剂物质的量分数为5%的条件下,纳米多孔钯可以高效催化亚胺化合物的加氢还原反应,高选择性、高产率地生成一系列仲胺,仲胺的产率在93%~96%之间.该反应官能团兼容性好,底物范围广,带有甲基、甲氧基、氰基和羟基等基团的亚胺都可以顺利发生还原反应生成相应的仲胺.催化剂重复使用5次后,活性未出现明显降低.     

Ionic liquid-phase asymmetric catalytic hydrogenation: hydrogen concentration effects on enantioselectivity

Molecular hydrogen is almost four times more soluble in the ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI·BF₄) than in its hexafluorophosphate (BMI·PF₆) analogue at the same pressure. The Henry coefficient solubility constant for the solution BMI·BF₄/H₂ is K=3.0×10⁻³ mol L⁻¹ atm⁻¹ and 8.8×10⁻⁴ mol L⁻¹ atm⁻¹ for BMI·PF₆/H₂, at room temperature. The asymmetric hydrogenation of (Z)-α-acetamido cinnamic acid and kinetic resolution of (±)-methyl-3-hydroxy-2-methylenebutanoate by (−)-1,2-bis((2R,5R)-2,5-diethylphospholano)benzene(cyclooctadiene)rhodium(I) trifluoromethanesulfonate and dichloro[(S)-(−)-2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl]ruthenium(II) complexes immobilised in BMI·PF₆ and BMI·BF₄ were investigated. Remarkable effects in the conversion and enantioselectivity of these reactions were observed as a function of molecular hydrogen concentration in the ionic phase rather than pressure in the gas phase.