Improvement of the Synthesis of Chiral Non-Racemic Bicyclic Lactams in the Piperidin-2-ones Series

Bicyclic lactams 8 have been prepared in enantiomerically pure form from the corresponding amino esters 5 and glutaric anhydride. The key step is the reduction of imides 7 in methanol. Selective reduction of 8 furnished N-substituted lactams 9.     

Electroreduction of a Sodium Salt of 4-Nitrosodiphenylamine: Effect of the Technological Solution Components

Two methods of preparation of 4-aminodiphenylamine (I) are compared: by electrochemical reduction of an alkaline solution of 4-nitrosodiphenylamine (II), extracted from a technological solution, and by electrolysis of the solution itself, which contains, apart from the nitroso compound, methanol and NaCl. By voltammetry and preparative electrosynthesis it is shown that the lower reduction rate of the technological solution of the Na salt of II is due to inhibiting effects of methanol and NaCl. Tetraalkylammonium cations, decreasing the limiting reduction current of II, do not affect the electrosynthesis rate when the generated I is continuously extracted into a water-immiscible solvent.     

Reduction of 2-amino-1-(4-nitrophenyl)-1 H-pyrido[3,2-b]indole-3-carbonitrile by sodium borohydride and sodium cyanoborohydride

The reduction of pyridoindole derivative 1 by sodium borohydride in methanol gives 4,5-dihydropyridoindole 2. On treatment of 5H-pyrido[3,2-b]indolium chloride 3 with sodium cyanoborohydride in methanol in the presence of hydrogen chloride, reduction of the pyridine ring is accompanied by reduction of the CN group, resulting in the formation of tetrahydropyridoindole 4. Compound 4 reacts with DMF dimethyl acetal to yield amidine 6, and refluxing of 4 with acetic anhydride results in tetrahydropyridine ring cleavage yielding indolylacrylonitrile 9. The hydrochloride and chloride of compounds 4 and 6 were obtained     

Catalytic behavior of a polynuclear Mg-Mo complex and nitrogenase active site (FeMoco) isolated from the enzyme in reactions with C2H2, N2, and CO: A comparative study

In order to identify common and distinctive features in the catalytic behavior of natural and artificial nitrogen-fixation clusters, the kinetics of the catalytic reduction of C₂H₂ in the presence of Mg-Mo-cluster (1) was investigated and compared with the kinetics of acetylene reduction catalyzed by the cluster FeMoco (2) isolated from the enzyme nitrogenase we studied previously. The reactions were conducted in the presence of Zn/Hg and Eu/Hg as reducing agents and PhSH and C₆F₅SH as proton donors, i.e., under the same conditions as had been used in the case of 2. Both polynuclear Mg-Mo-complex and the europium amalgam-reduced FeMoco have multiple interdependent binding sites for substrates and/or inhibitors. Carbon monoxide inhibits the acetylene reduction much less efficiently in systems with cluster 1 than in systems with cluster 2, although the type of inhibition is mixed in both systems: CO binds to multiple sites of the cluster and affects both C₂H₂ complexation to the reduced cluster and decomposition of the catalyst-substrate complex to give the products. Unlike isolated FeMoco, the Mg-Mo-cluster efficiently catalyzes the reduction of molecular nitrogen. The reaction is greatly inhibited by acetylene, while no inhibiting effect of N₂ is observed in acetylene reduction, as was found earlier for a system with the natural cluster as the catalyst. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 766–774, May, 2006.     

二硫桥键钴卟啉二聚体的合成与电催化氧还原性能

成功合成了二硫桥键相连的钴卟啉二聚体2Co。通过循环伏安电化学方法测试,在无水二氯甲烷溶剂中,钴卟啉二聚体展示了3个氧化和2个还原峰,表明此钴卟啉二聚体可以稳定多重负/正电荷。详细研究了在酸性条件下的钴卟啉二聚体的电催化氧还原性能。钴卟啉二聚体的电催化氧还原显示了高稳定性和高活性,测得转移电子数为3.5~3.6之间。钴卟啉二聚体的电催化氧还原性能说明通过二硫键对钴卟啉单体二聚化可以提高钴卟啉的电催化氧还原性能。     

HYDROGENATION OF A DELOCALIZED DIIMINATE SIX-MEMBERED CHELATE RING IN TETRAAZAMACROCYCLIC NICKEL(II) COMPLEXES BY SODIUM BOROHYDRIDE IN WATER—EFFECT OF PROTONATION-DEPROTONATION EQUILIBRIA AND STEREOSELECIVE REDUCTION

Abstract

Charge delocalized diiminate six-membered chelate rings in the 5,7-dimethyl-1,4,8,11-tetraazacyclotetradecane-4,6-dienatonickel(II) ion(1) and the α,α′-bis(5,7-dimethyl-1,4,8, 11-tetraazacyclotetradeca-4,6-dienato-6-yl)-xylenedinicke(II) ion(2) were hydrogenated in aqueous media by sodium borohydride. In the reduction reactions, control of the pH of the reaction mixture was essential, and the pH of the solution was kept during the reaction at 3 and at 5–6 for hydrogenations of 1 and 2, respectively. The delocalized diiminate chelate ring is in protonation-deprotonation equilibrium with the β diimine form and the pK_a of the equilibrium for 2 was determined to be 9.0 for 2a (o-xylylene bridged complex), 9.3 for 2b (m-xylylene bridged complex), and 10.0 for 2c (p-xylylene bridged complex). The appropriate pH values in the hydrogenation reactions were based on the pK_a′s. X-ray structure analyses on two reduction products of 1 show that the chirality of the two asymmetric carbons in the cyclam ring is of the meso-form in the major reduction product whereas that in the minor product is of the racemic form. In the major reduction product of 2, two chiral carbons in each cyclam ring take the meso-form.     

Electrochemical reduction of 5-halo-5-nitro-1,3-dioxanes and 2-halo-2-nitro-1,3-propanediols

The character of the first stage of reduction of 5-X-5-nitro-1,3-dioxanes 1—10 and 2-X-2-nitro-1,3-propanediols 11 and 12 is independent of the nature of halogen (X = Br, Cl) and substituents in position 2 of the dioxane cycle. The transfer of two electrons to a molecule of compound 1—12 is accompanied by the anionoid elimination of halogen and formation of the anion of nitronic acid. The high mobility of halogen is mainly due to the acceptor nitro group capable of further transformations in the -position to halogen. The direction of further reduction involving the electron transfer to electrochemically active groups in the aromatic fragment of the molecule is determined by the nature of these groups. Chloro-, bromo-, and iodophenyl-substituted derivatives 4, 5, and 8—10 are reduced as typical halobenzenes. In the case of nitrophenyl-substituted compounds 3 and 7, the dioxane cycle opens to form dianions of p- and m-nitrobenzaldehydes along with the reduction of the nitroso group through the stages of formation of the radical anion and radical anion of the nitroso group. The radical anions of the nitro and nitroso derivatives were identified by ESR.     

一种新的合成12-氧代-1,15-十五内酰胺的方法

设计了一种新的合成12-氧代-1,15-十五内酰胺(4)的方法, 即以α-硝基环十二酮(1)为原料, 经与丙烯腈的Michael加成, 氰基选择性还原为氨基后扩环, 再经Nef反应合成了4, 总收率为28%.     

Synthesis, crystal structure, and reduction of bis(2-phenylindenyl)hafnium dichloride

Reduction of the bent-sandwich [·⁵-(Ph)Ind]₂HfCl₂ complex (1) (where (Ph) Ind is the 2-phenylindenyl anion) in a THF medium was studied by low-temperature cyclic voltammetry. Complex1 is stable in THF at a temperature lower than −50°C and undergoes reversible one-electron reduction to radical anion1 ^{. −}. Further one-electron reduction of1 ^{. −} to dianion1 ²⁻ is accompanied by the elimination of two Cl⁻ ions to form the bisindenyl sandwich [·⁵-(Ph)Ind]₂Hf complex (2). This complex can undergo reversible one-electron reduction to the corresponding radical anion2 ^{. −}, which is stable within the cyclic voltammetry time scale. AtT=−30°C in a THF solution, complex1 was reduced to a diamagnetic (apparently, binuclear) Hf^III complex, which was characterized by cyclic voltammetry. Synthesis and the crystal structure of complex1 are reported. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2161–2165, December, 1997.     

Sulfur ylides. 11. Selected chemical transformations of 1-methylthio-3,4-dihydropyrido[2,1-a]isoindole-2,6-dione

The reaction of 1-methylthio-3,4-dihydropyrido[2,1-a]isoindole-2,6-dione (2) with NaBH₄ led to reduction of the keto group to the hydroxy group. The reaction with the use of LiAlH₄ resulted in complete reduction of the carboximide group, reduction of the keto group to the hydroxy function, and reduction of the double bond accompanied by desulfurization. The reaction of indolizidinedione 2 with Zn afforded a reductive desulfurization product. The reactions of 2 with hydrazine hydrate, hydroxylamine, and formamide proceeded according to a mechanism typical of the keto group to give hydrazone, oxime, and the formyl derivative, respectively. Oxidation of the thiomethyl group of the starting compound with Bu^tOOH gave rise to sulfone or sulfoxide depending on the amount of the oxidizing agent used.     

二茂铁功能化的金属有机大环模拟氢化酶光催化硝基还原

使用二茂铁构筑了2个新型金属有机大环： M_Cu和M_Fe。2个大环化合物有效猝灭了有机染料的荧光,并可触发光致电子转移。较低的还原电位导致M_Cu在光催化质子还原和硝基还原2个反应中表现出更好的催化性能。底物的大尺寸导致硝基还原过程的效率降低。用Michaelis-Menten机理对光催化体系进行了验证,揭示了底物与催化剂之间相互作用的重要性。     

二茂铁功能化的金属有机大环模拟氢化酶光催化硝基还原

使用二茂铁构筑了2个新型金属有机大环：M_Cu和M_Fe。2个大环化合物有效猝灭了有机染料的荧光,并可触发光致电子转移。较低的还原电位导致M_Cu在光催化质子还原和硝基还原2个反应中表现出更好的催化性能。底物的大尺寸导致硝基还原过程的效率降低。用Michaelis-Menten机理对光催化体系进行了验证,揭示了底物与催化剂之间相互作用的重要性。     

用铝-镍合金还原1-萘酚反应的再研究

文献曾报道以铝-镍合金为还原剂, 在稀碱水溶液中, 可以将1-萘酚(1)以高收率还原为5,6,7,8-四氢-1-萘酚(2). 本研究工作发现, 在相同的条件下该反应除了生成少量2外, 3,4-二氢-2H-萘-1-酮(3)和1,2,3,4-四氢-1-萘酚(4)为主要产物, 该结果明显不同于文献报道, 对反应产物分布及其可能机理进行了探讨. 该还原反应体系为3,4-二氢-1(2H)-萘酮(3)和1,2,3,4-四氢-1-萘酚(4)的合成提供了一条新途径.     

Synthesis, electrochemistry, thin-layer UV-vis and fluorescence spectroelectrochemistry of a new salicylaldimine ligand and its copper complex

The new asymmetric, fluorescent Schiff-base ligand, N-(pyrene)-salicylaldimine (L), and its copper complex having an ONNO donor set, [Cu(L) ₂ ], were synthesized and characterized using elemental analysis, IR, UV-vis, ¹H and ¹³C-NMR spectroscopies. Their electrochemical and spectroelectrochemical behaviors were investigated in a detail by using cyclic voltammetry (CV), square wave voltammetry (SWV), in-situ UV-vis, and fluorescence spectroelectrochemistry. The formation of the complex was monitored by the in-situ fluorescence technique based on the quenching of the fluorescence-probe ligand. Electrochemical studies showed that L exhibits a single irreversible reduction process. However, the SWV indicated that this process was not totally irreversible in the time scale of the measurement. The cathodic peak potential of the reduction process occurred at E _pc = −1.35 V vs Ag/AgCl (scan rate: 0.025 Vs⁻¹). On the other hand, [Cu(L) ₂ ] showed one quasi-reversible one-electron reduction process in the scan rates of 0.025–0.50 Vs⁻¹, which was assigned to metal-based one-electron process; [Cu(2+)(L)₂] + e⁻ → [Cu(+)(L)₂]⁻. The value of half-wave potential (E _1/2) of the reduction process was −0.54 V vs Ag/AgCl (scan rate: 0.025 Vs⁻¹). The time-resolved spectra showed, when the potential (E _app = −1.60 V) was applied in a thin-layer cell, that the main and shoulder bands of (L) at 385, 336, and 407 nm almost disappeared and a new band at 443 nm with a shoulder formed during the reduction process. No change was observed on the final spectrum of the totally reduced ligand for long period under nitrogen atmosphere, which indicated that the singly reduced species remained stable and was not accompanied by a chemical reaction in the time scale of the spectroelectrochemical measurement. The spectral changes during the reduction process of [Cu(L) ₂ ] confirmed the metal-centered reduction process. The fluorescence intensity of L decreased during the reduction process in the thin-layer cell, as result of the perturbation of the conjugated system of the reduced species.     

Thermal and Catalytic Diels-Alder Reactions Between (2E)-4, 5,6-Tri-O-acetyl-2,3-dideoxy-aldehydo-D-erythro -Hex-2-Enose and Cyclopentadiene

Abstract

Thermal and catalytic reactions between (2E)-4,5,6-tri-O-acetyl-2,3-dideoxy- aldehydo- d-erythro-hex-2-enose (1) and cyclopentadiene led, in each case, to the four stereoisomeric 5-formyl-6-(1,2,3-tri-O- acetyl-d-erythro-triol-1-yl)bicyclo[2.2.1]hept-2-enes (2-5). The role of the catalysts is discussed, and the face selectivity is rationalized in terms of both steric and electrostatic arguments. Upon subsequent sodium borohydride reduction, iodination, and zinc reduction, the adducts 2-5 were converted to their respective primary alcohols 6-9, that could be separated by column chromatography. Sequential basic deacetylation, oxidative cleavage of the sugar side-chain with sodium metaperiodate, and reduction with sodium borohydride, yielded the previously known (5R,6R)- or (5S, 6S)-bis(hydroxymethyl)norbornene-diols 12 or 13, thus establishing the C-5 and C-6 absolute configurations of their synthetic precursors.     

Synthesis and pH-sensitive redox properties of 1,10-phenanthroline-5,6-dione complexes

Synthesis and pH-sensitive electrochemical properties of three complexes, [Cu(PD)₃] · (ClO₄)₂ · 2.25CH₃CN · 6H₂O (1), [Cu(PD)(DMSO)Cl₂] · DMSO · H₂O (2) and [Co(PD)₃] · (ClO₄)₂ · CH₃CN · 2H₂O (3) (PD=1,10-phenanthroline-5,6-dione), are reported. Single-crystal X-ray diffraction of the complexes suggest that the structure of 1 is orthorhombic, 2 triclinic and 3 orthorhombic. The electrochemical properties of free PD and the three complexes in phosphate buffer solutions in a pH range between 2 and 9 have been investigated using cyclic voltammetry. The redox potentials of these compounds are strongly dependent on the proton concentration in the range ?0.3 V ～ 0.4 V versus SCE (saturated calomel reference electrode). The reduction behavior of PD can be described from quinone species to semiquinone anion then to the fully reduced dianion. At pH < 4, the reduction of PD proceeds via 2e^?/3H⁺ processes, while at pH > 4, the reduction of PD proceeds via 2e^?/2H⁺. For all complexes, the N–N chelate PD ligand is electrochemically active and underwent step reduction via 2e^?/2H⁺.     

Complexes of rhodium carbonylchloride and phosphorus(iii) cyanides in mediated electrochemical reduction of 2-carbomethoxy-2-methyl-1,1-dichlorocyclopropane

Electrochemical reduction of the complexes Rh(CO)ClL₂ [L = (EtO)₂PCN (1), Ph₂PCN (2)] and Rh₂(CO)₄L [L = P(CN)₃ (3), (4)] and their catalytic properties in electrochemical reduction of 2-carbomethoxy-2-methyl-1,1-dichloro-cyclopropane were studied. The catalytic electroreduction of a substrate at the reduction potentials of the central ion was developed for complexes2–4. This process is accelerated substantially for complexes2 and3 in the presence of anthracene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1970–1972, October, 1995.     

Cubane derivatives 7. Synthesis and molecular structure of 4-bromo-1-hydroxymethylcubane

The present study concerned with reduction of methyl 4-bromocubanecarboxylate (1) with lithium aluminum hydride and aluminum hydride in THF. An efficient procedure was developed for the synthesis of 4-bromo-1-hydroxymethylcubane (2) based on reduction of compound 1 with aluminum hydride under mild conditions. The structure of 2 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1461–1464, June, 2005.     

Inhibition of Reduction Current of Oxygen by Cysteine and Glutathione at Smooth Platinum Electrodes

Abstract

The reduction of molecular oxygen is inhibited by the chemisorption of cysteine and glutathione on the smooth platinum electrode. The cathodic current of the molecular oxygen reduction is dependent on the concentration of both substances.     

1,3-Diphenylpropane-1,3-diamines XI. Conversion of a 3-hydroxy-1,3-diphenylpropan-1-one to 1,3-diphenylpropane-1,3-diamines

Summary Highly diastereoselective BH₃/THF syn-reduction of the 3-hydroxy-1,3-diphenylpropan-1-one/BBr₃ complex3/BBr₃ (cf.Sarko) afforded themeso-diol4, whereas racemate5 was obtained by BH₃/THF reduction without complexation. Mesylation, exchange of mesylate by azide, and reduction with SnCl₂/thiophenol led to the diamines10 and11 which were also produced by reductive N-N cleavage of the 4,5-dihydropyrazole13.Dedicated to Prof. Dr.G. Wurm, Berlin, on the occasion of his 60^th birthday