Synthesis and characterisation of anionic and neutral gallium(I) N-heterocyclic carbene analogues

A high yield synthesis of a new, extremely bulky anionic gallium(I) N-heterocyclic carbene analogue, [(DAB*)Ga:](-) (DAB* = {N(Ar*)C(H)}(2), Ar* = C(6)H(2){C(H)Ph(2)}(2)Me-2,6,4) has been developed and four monomeric sodium complexes of the heterocycle have been crystallographically characterised. The gallium(I) heterocycle has been utilised in the preparations of the heteroleptic zinc and cadmium gallyl complexes, [(DAB*)GaMX(tmeda)] (M = Zn or Cd, X = Br or I), which were crystallographically characterised. In addition, [(DAB*)Ga:](-) was oxidatively coupled to give the diamagnetic digallane(4), [(DAB*)GaGa(DAB*)]. The moderate yield synthesis of the six-membered gallium(I) heterocycle, [((But)MesNacnac)Ga:] ((But)MesNacnac = [(MesNCBu(t))(2)CH](-), Mes = mesityl), is described, and the compound found to be a monomer in the solid state by an X-ray crystallographic analysis. A low yield by-product from this synthesis, [Ga(5)I(4)((But)MesNacnac)(3)], was also isolated and shown by X-ray crystallography to be a rare example of a compound bearing a group 13 metal-metal bonded chain stabilised by β-diketiminate ligands. A preliminary analysis of the bonding in the compound was carried out using DFT calculations.     

Efficient Synthesis of Triarylamines Catalyzed by Copper(I) Diazabutadiene Complexes

Cuprous chloride was coordinated by diazabutadiene (DAB‐R) ligands to form Cu(I)‐(DAB‐R) complexes, most of which have a 1:1 ratio of Cu to DAB‐R as reported. In the case of a special DAB‐ⁱPP, N,N′‐bis(2,6‐diisopropylphenyl)‐1,4‐diaza‐1,3‐butadiene, an unexpected composition of complex was found with the formula Cu(I)Cl(DAB)₂. When employed as catalyst for triarylamine synthesis from the coupling of aryl halides with primary and secondary arylamines, the new Cu(I)‐(DAB‐ⁱPP) complex displayed high efficiency.     

Reaction of 1,3-dimethyl-5-acetyl-barbituric acid (DAB) with primary amines. Access to intermediates for selectively protected spermidines

The ability of 1,3-dimethyl-5-acetyl-barbituric acid (DAB) to react with primary amines in a chemoselective fashion was applied to the synthesis of a selectively protected spermidine.     

Ionic Self‐Assembled Platform of Perylenediimide–Sodium Dodecylsulfate for Detection of Spermine in Clinical Samples

The detection and quantification of spermine in clinical practice is important for early diagnosis of many diseases. Chromatographic and immunoassay‐based methods are commonly used. However, a fluorescence‐based assay could provide real‐time detection. Herein, the synthesis and aggregation properties of a dicationic perylene probe (N ¹‐dodecyl‐N ³‐(4‐phenyl)benzimidazolium‐functionalized perylenediimide ( DAB‐PDI )) used to develop a fluorescent “turn‐on” ensemble for the detection of spermine are discussed. The fluorescence of DAB‐PDI (10 μm , Φ =0.55) is efficiently quenched by negatively charged sodium dodecylsulfate (SDS) through the formation of ionic self‐assembled aggregates (charge ratio of negative (N) in SDS to positive (P) in DAB‐PDI (N/P)=9). This negatively charged ionic self‐assembly between DAB‐PDI and SDS has been characterized by using photophysical, microscopic, dynamic light scattering, isothermal titration calorimetry, and HRMS techniques. The addition of spermine to this ensemble solution results in the breakdown of the DAB‐PDI –SDS ensemble owing to strong binding of spermine with SDS and, as a result, the fluorescence of DAB‐PDI is recovered. This ensemble exhibits high sensitivity and selectivity for spermine detection in water, urine, and blood serum. The lowest limit of detection is 27.5 nm , which is at least about 36 times lower than that required for early diagnosis of cancer (1 to 10 μm for urinary spermine).     

First-Principles Microkinetic Study of Methanol Synthesis on Cu(221) and ZnCu(221) Surfaces

First-principle based microkinetic simulations are performed to investigate methanol synthesis from CO and CO₂ on Cu(221) and CuZn(221) surfaces. It is found that regardless of surface structure, the carbon consumption rate follows the order:CO hydrogenation > CO/CO₂ hydrogenation > CO₂ hydrogenation. The superior CO hydrogenation activity mainly arises from the lower barriers of elementary reactions than CO₂ hydrogenation. Compared to Cu(221), the introduction of Zn greatly lowers the activity of methanol synthesis, in particularly for CO hydrogenation. For a mixed CO/CO₂ hydrogenation, CO acts as the carbon source on Cu(221) while both CO and CO₂ contribute to carbon conversion on CuZn(221). The degree of rate control studies show that the key steps that determine the reaction activity of CO/CO₂ hydrogenation are HCO and HCOO hydrogenation on Cu(221), instead of HCOOH hydrogenation on CuZn(221). The present work highlights the effect of the Zn doping and feed gas composition on methanol synthesis.     

Monitoring of the formation of binuclear ruthenium carbonyl complexes during reactions by means of high performance liquid chromatography

Reversed-phase high performance liquid chromatography has been used to monitor the reactions of Ru₃(CO)₁₂ with 1,4-diazabutadiene (DAB) and of Ru₂(CO)₆ (DAB) with DAB. The kinetic data show that the formation of an intermediate in the former reaction is the rate determining step, which is first order in Ru₃(CO)₁₂ as well as in DAB. The reactivity depends strongly on the type of substituent on DAB. Exchange of free and coordinated ligands (isopropyl DAB and tert-butyl DAB) is demonstrated in the reaction of Ru₂(CO)₆ (DAB) with DAB. A reversible reaction is proposed to account for this exchange.     

The Thermodynamics of Translesion DNA Synthesis Past Major Adducts of Enantiomeric Analogues of Antitumor Cisplatin

The Pt^II-coordination complex [PtCl₂(DAB)] (DAB=2,3-diaminobutane) belongs to a class of cytotoxic cisplatin analogues that contain chiral diamine ligands. Enantiomeric pairs of these compounds have attracted particular interest because they have different effects on different DNA conformations, which, in turn, influences the binding of damaged-DNA-processing enzymes that control downstream effects of the adducts, and thus exhibit different biological activities of the enantiomers. Herein, we studied the translesion synthesis across the major 1,2-d(GG) intrastrand cross-link formed by the R,R and S,S enantiomers of [Pt(DAB)]²⁺ in the TGGT sequence by using the enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. We also employed differential scanning calorimetry (DSC) to measure the thermodynamic changes associated with replication-bypass past 1,2-d(GG) adducts of the [Pt(DAB)]²⁺ enantiomers. In the sequence TGGT, the 1,2-d(GG) intrastrand cross-links that were formed by the enantiomeric pairs of [Pt(DAB)]²⁺ inhibited DNA polymerization in a chirality-dependent manner. The thermodynamic data helped to understand the effect of the alterations in thermodynamic stability of DNA caused by the Pt-d(GG) adducts upon DNA polymerization across these lesions. Moreover, these data can possibly explain the influence of these alterations on the ability of many DNA polymerases to bypass adducts of antitumor platinum drugs. These results also highlighted the usefulness of DSC in evaluating the impact of DNA adducts of platinum-coordinated compounds on the processing of these lesions by damaged-DNA processing-enzymes.     

CO2／H2和（CO／CO2）＋H2低压合成甲醇催化过程的本质

通过在Ｃｕ／ＺｎＯ／Ａｌ２Ｏ３催化剂上ＣＯ２＋Ｈ２，ＣＯ＋Ｈ２和（ＣＯ／ＣＯ２）＋Ｈ２催化反应动力学研究对合成甲醇动力学和反应机理进行了细致分析，提出合成甲醇的反应机理，解释了在（ＣＯ／ＣＯ２）＋Ｈ２合成甲醇过程中少量ＣＯ２的作用及合成甲醇的直接碳源。     

Composition of hydrofullerene mixtures produced by C(60) reaction with hydrogen gas revealed by high-resolution mass spectrometry

Complex solid hydrofulleride mixtures were synthesized by prolonged hydrogenation of C(60) at 120 bar hydrogen pressure, 673 K temperature, and different reaction periods. The high degree of hydrogenation was confirmed by infrared spectroscopy and X-ray diffraction. The identity of hydrogenation products was determined by high-resolution field desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry. Despite partial gas-phase fragmentation of hydrofullerene ions during mass analysis, the data suggest that the synthesized mixtures consist of mostly C(58-60)H(x) hydrofullerenes. Increasing the duration of hydrogenation results in synthesis of C(59)H(x) and C(58)H(x) as major products. Possible hydrofullerene fragmentation pathways during both material synthesis and mass spectrometric analysis are discussed. Gas-phase fragmentation in the mass spectrometer arises from hydrofullerene ions C(60)H(x)(+) with x > 40 and C(59)H(44)(+) with drastically decreased molecular stability relative to the known C(60)H(36).     

Development of new methods in organic synthesis and their applications to the synthesis of biologically interesting natural products

2,6-Dimethyl-9-Aryl-9-phosphabicyclo[3.3.1]nonanes (9-PBN and 9-NapBN) and the chiral diaminophosphine oxides (DIAPHOXs) derived from aspartic acid have been introduced as useful ligands and preligands, respectively, for transition metal-catalyzed asymmetric synthesis. anti-Selective asymmetric hydrogenation of α-amino-β-ketoesters using Ru-, Rh-, Ir-, and Ni-catalysts through dynamic kinetic resolution have been developed for the first time, producing efficiently important anti β-hydroxy-α-amino acids. The total synthesis of several biologically active natural products was achieved by use of the transition metal-catalyzed reaction using DIAPHOX, anti-selective asymmetric hydrogenation, and reactions developed by us. Synthesis of tangutorine, an antitumor indole alkaloid, has been enantioselectively achieved for the first time. Enantioselective synthesis of a martinelline chiral core was accomplished using the asymmetric tandem Michael-Aldol reaction as a key step developed by us. This synthesis represents the formal total synthesis of martinelline and martinellic acid. Papuamide B was synthesized through the elucidation of unknown stereostructures by using the anti-selective asymmetric hydrogenation and reactions developed by us.     

A highly selective arene hydrogenation catalyst that operates in ionic liquid

The synthesis and structural characterization of [Ru(eta(6)-p-cymene)(eta(2)-TRIPHOS)Cl][PF(6)] is described. The complex is a highly active, homogeneous arene hydrogenation catalyst that is selective toward the hydrogenation of aromatic rings in preference to alkenes, as demonstrated by the hydrogenation of allylbenzene to allylcyclohexane. The catalyst operates in both dichloromethane and ionic liquids and undergoes no decomposition in the latter solvent.     

Diazabutadiene: a simple and efficient ligand for copper-catalyzed N-arylation of aromatic amines

Diazabutadienes (DABs) were chosen as ancillary ligands in the Cu-catalyzed C–N coupling reaction for the synthesis of triarylamines. A combination of CuI/DAB (1) [1: N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene] was found to be an efficient catalyst system for N-arylation of diarylamines and anilines with aryl iodides, affording the desired products in good to excellent yields.     

3 d Transition Metal‐Catalyzed Hydrogenation of Nitriles and Alkynes

Selective hydrogenation of nitriles and alkynes is crucial considering the vast applications of reduced products in industries and in the synthesis of bioactive compounds. Particularly, the late 3d transition metal catalysts (manganese, iron, cobalt, nickel and copper) have shown promising activity for the hydrogenation of nitriles to primary amines, secondary amines and imines. Similarly, semihydrogenation of alkynes to E‐ and Z‐alkenes by 3d metals is adequately successful both via the transfer hydrogenation and by using molecular hydrogen. The emergence of 3d transition metals in the selective synthesis of industrially relevant amines, imines and alkenes makes this protocol more attractive. Herein, we provide a concise overview on the late 3d transition metal‐catalyzed hydrogenation of nitriles to amines and imines as well as semihydrogenation of alkynes to alkenes.     

Diastereoselective concise syntheses of the polyhydroxylated alkaloids DMDP and DAB

A diastereoselective concise synthesis of the iminosugars DMDP and DAB is presented starting from l-xylose and affording the two alkaloids in good yields of 35% and 22% over seven and eight steps, respectively. The Petasis borono–Mannich reaction of 3,5-di-O-benzyl-l-xylofuranose with benzylamine and (E)-styrylboronic acid served as the nitrogen-introducing key step furnishing the new C–N bond in an entirely diastereoselective manner. A chemo- and regioselective O-mesylation followed by an intramolecular S_N2-cyclisation allowed the formation of the pyrrolidine ring. Ozonolysis of the styryl double bond and subsequent reduction to form the C-5 hydroxymethyl substituent followed by hydrogenolysis of the benzyl protecting groups concluded the DMDP synthesis. Furthermore, an unexpected fragmentation process during the ozonolysis reaction also gave access to the C-5 decarbinolated DMDP derivative DAB.     

低温加氢催化剂的设计:理论与实践(英文)

简要总结了我们在C=C及C=O双键低温加氢双金属催化剂方面的最新研究成果.首先,我们以环己烯加氢为探针反应,证明了平行使用多种研究手段的重要性,包括单晶表面的基础研究与DFT计算,多晶表面的合成与表征,负载型催化剂的制备与性能测试等.其次,总结了双金属催化剂在其他加氢反应,如丙烯醛C=O双键的选择性加氢,苯的低温加氢,以及乙炔的选择性加氢等反应中的应用.最后,讨论了利用金属碳化物代替贵金属Pt以减少双金属催化剂中Pt用量的可能性.     

Synthesis of (S)-7-amino-5-azaspiro[2.4]heptane via highly enantioselective hydrogenation of protected ethyl 1-(2-aminoaceto)cyclopropanecarboxylates

Highly effective asymmetric hydrogenation of protected ethyl 1-(2-aminoaceto)cyclopropane carboxylates in the presence of [RuCl(benzene)(S)-SunPhos]Cl was realized, and high enantioselectivities (up to 98.7% ee) were obtained. This asymmetric hydrogenation provides a key intermediate for the enantioselective synthesis of (S)-7-amino-5-azaspiro[2.4]heptane moiety of quinolone antibacterial agents.     

Synthesis and characterization of cationic selenium-nitrogen heterocycles from tert-butyl-DAB (DAB = 1,4-di-tert-butyl-1,3-diazabutadiene) and SeX4 via the reductive elimination of X2 (X = Cl, Br): a distinct contrast with tellurium

The synthesis and comprehensive characterisation of a series of 1,2,5-selenadiazolium salts, which were generated from the direct reaction between the neutral bidentate ligand tert-butyl-DAB and a variety of heavy chalcogen halides, are reported. The formation of the cationic heterocycle from the reaction of SeX4 (X = Cl, Br) and the ligand results in a two electron redox process where the chalcogen undergoes a two electron reduction concomitant with the elimination of X2, the oxidation by-product. A reaction pathway for this chemistry has been proposed necessitating several key intermediates. These species have been synthesized and used in a stepwise series of transformations that strongly supports this very unusual reactivity for the chalcogens. In contrast, the reaction between tert-butyl DAB and TeX4 (X = Cl, Br, I), does not result in redox, rather an octahedral Te(iv) x DAB complex is formed or no reaction was observed.     

CuO-ZnO-ZrO2的柠檬酸燃烧法制备及其催化CO2加氢合成甲醇的性能

采用柠檬酸燃烧法制备了CuO-ZnO-ZrO2(CZZ)催化剂,并将其用于CO2加氢合成甲醇反应.按推进剂化学原理对燃烧反应进行了分析,并采用热重-差热分析(TG-DTA)技术记录了其燃烧行为.采用X射线衍射(XRD)、氮吸附、程序升温还原(TPR)及氧化亚氮(N2O)反应吸附技术对制得的催化剂进行了表征.结果表明:柠檬酸燃烧法的燃烧过程比较温和,燃料用量对催化剂物化和催化性能的影响不大,并结合燃烧反应的特点进行了解释.此外,还对三种燃料(柠檬酸、尿素和甘氨酸)的用量与CZZ性能之间的关系进行了比较,表明柠檬酸作燃料具有更好的工艺可控性.柠檬酸燃烧法是一种简单、快速且有效的制备CZZ催化剂的方法.     

Highly selective asymmetric hydrogenation using a three hindered quadrant bisphosphine rhodium catalyst

A concise synthesis of both enantiomers of ligand 2 and rhodium complex 5 is presented. The crux of the synthesis is a chiral HPLC separation of the enantiomers of 4. Rhodium complex 5 possesses three hindered quadrants in the steric environment within which a substrate binds. Evidence is presented that this configuration leads to high enantioselectivity (>99% ee) for rhodium-catalyzed asymmetric hydrogenation of alpha-acetamido dehydroamino acids, 6a-e. High enantioselectivities are also reported for the hydrogenation of a substrate precursor, 8, of pharmaceutical candidate, pregabalin. Advantages for large-scale hydrogenation of 8 using catalyst 5a vs Rh-Me-DuPhos are discussed.     

低温加氢催化剂的设计: 理论与实践

简要总结了我们在C=C及C=O双键低温加氢双金属催化剂方面的最新研究成果. 首先, 我们以环己烯加氢为探针反应, 证明了平行使用多种研究手段的重要性, 包括单晶表面的基础研究与DFT计算, 多晶表面的合成与表征, 负载型催化剂的制备与性能测试等. 其次, 总结了双金属催化剂在其他加氢反应, 如丙烯醛C=O双键的选择性加氢, 苯的低温加氢, 以及乙炔的选择性加氢等反应中的应用. 最后, 讨论了利用金属碳化物代替贵金属Pt以减少双金属催化剂中Pt用量的可能性.