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Despite six decades use of aluminum as a galvanic (sacrificial) anode, there remains a need for a better understanding of the underlying mechanisms for enhancing its efficient performance in cathodic protection systems. A few mechanisms have been proposed for the role of indium in the activation of Al-Zn-In anodes and there appears to be no general agreement on whether this element plays its depassivating role by modifying the bulk microstructure of the anode, chemical composition of its surrounding electrolyte or directly through doping the structure of the passive oxide film. These mechanisms have been critically reviewed to achieve a more comprehensive understanding of the role of indium in such applications. Moreover, the novel solidification processing called controlled diffusion solidification (CDS) has been introduced as an efficient way to surmount the poor castability of the anode alloy without any need for the addition of elements with detrimental effects on the electrochemical properties of the anode.

Synergism among several intertwined catalytic cycles allows for selective, room temperature oxidation of primary amines to the corresponding nitriles in 85-98% isolated yield. This metal-free, scalable, operationally simple method employs a catalytic quantity of 4-acetamido-TEMPO (ACT; TEMPO=2,2,6,6-tetramethylpiperidine N-oxide) radical and the inexpensive, environmentally benign triple salt oxone as the terminal oxidant under mild conditions. Simple filtration of the reaction mixture through silica gel affords pure nitrile products.

A scalable, high yielding, rapid route to access an array of nitriles from aldehydes mediated by an oxoammonium salt (4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate) and hexamethyldisilazane (HMDS) as an ammonia surrogate has been developed. The reaction likely involves two distinct chemical transformations: reversible silyl-imine formation between HMDS and an aldehyde, followed by oxidation mediated by the oxoammonium salt and desilylation to furnish a nitrile. The spent oxidant can be easily recovered and used to regenerate the oxoammonium salt oxidant.

The reaction mechanism is investigated by computational calculations and involves a hydride transfer.

The synthesis, full characterization, photoreduction properties, and catalytic activity for the copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction of a copper(II)-DMEDA (N,N′-dimethylethylendiamine) complex is reported. Spectroscopic studies (UV/Vis, EPR) demonstrated that under daylight illumination highly effective copper(II) to copper(I) reduction occurs in this complex. These findings are in agreement with a high photoreduction quantum yield value of 0.22 in MeOH, and a value approaching unity as determined in THF. The reduction process, which can also be conducted by irradiation at 365 nm by using a standard TLC (thin layer chromatography) lamp, is ascribed to a highly efficient photoinduced electron transfer (PET) process mediated by the benzophenone photosensitizer present in the carboxylate counterion. Having deaerated the reaction mixture, the photogenerated copper(I) species proved to be highly active for the CuAAC reaction, demonstrated by reactions conducted with low catalyst loading (0.5 mol %) on a range of clickable protected and non-protected mono- and disaccharides. Once initiated, the reaction can be stopped at any time on introducing air into the reaction medium. Deoxygenation followed by irradiation restores the activity, making the copper(II)-DMEDA complex a switchable catalyst of practical value.

Bimolecular nucleophilic substitution reactions of alcohols are fundamentally important transformations in organic chemistry yet, to date, they are relatively underdeveloped with respect to catalysis. This Article describes the emerging area of catalytic SN2 reactions with specific emphasis on the design and development of phosphorus(V) and cyclopropenone-based catalytic SN2 reactions of alcohols.

A detailed study on the photoreduction of a copper(II) precatalyst to generate a highly reactive cuprous species for the copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction is presented.

Cyclopropenimine is an efficient and selective catalyst for Mannich reactions between glycine imines with aryl and aliphatic N-Boc-aldimines with high levels of enantio- and diastereoselectivity.

This review covers the preparation, physical properties, and applications of cyclopropenium ions bearing one, two, or three amino substituents. It provides a description of the most reliable methods to access these unique structures as well as a discussion of the reactivity profiles of the common subtypes. 1 Introduction 2 Preparation 3 Properties 3.1 Stability 3.2 Redox Behavior 3.3 Ion Pair Strain 4 Reactions 5 Applications 5.1 Ionic Liquids 5.2 Metal Complexes 5.2.1 TDAC π-Complexes 5.2.2 BDAC σ-Complexes 5.2.3 Cyclopropenimine Ligands 5.2.4 BDAC–Phosphorus Ligands 5.3 Bronsted Bases 6 Conclusion

The presented method applies iBu3N as a base and diphenyl- (DPC) and dianisylcyclopropenones (DAC) as promoters and proceeds with high stereoselectivity and inversion of configuration.

This strategy relies on a conceptual change from traditional [2 + 2] cycloaddition/cycloreversion concepts towards a [3 + 2] manifold.

A novel and facile synthetic route to NH-2-(alkylsulfanyl)-1 H -pyrroles and N -alkyl-2-(alkylsulfanyl)-1 H -pyrroles is reported. This was achieved by deprotonation of allyl isothiocyanate with the superbasic pair lithium diisopropylamide and potassium tert -butoxide (1:1 molar mixture), followed by intramolecular ring closure, deprotonation of cyclic anion with a second equivalent of the superbase, and final sequential N-protolysis/S-alkylation or N,S-dialkylation of the formed N,S-centered pyrrol-2-ylsulfide dianion.

Tungsten borides are known to be very hard and metallic materials. Tungsten monoboride, WB, becomes superconducting at Tc = 4.3 K in the tetragonal modification and Tc = 2.8 K in the orthorhombic modification. The structures of the two WB modifications were revised based on X-ray and neutron powder diffraction. W2B4, formerly known as W2B5, also shows a superconducting transition at 5.4 K, which is suppressed for small grain samples.

Title compounds can be synthesized by stepwise one-pot reaction of aryl carboxylic acids with hydrazines followed by ring closure in the presence of thioxoacetate (IV).

Mixed-valence (MV) compounds are excellent model systems for the investigation of basic electron-transfer (ET) or charge-transfer (CT) phenomena. These issues are important in complex biophysical processes such as photosynthesis as well as in artificial electronic devices that are based on organic conjugated materials. Organic MV compounds are effective hole-transporting materials in organic light emitting diodes (OLEDs), solar cells, and photochromic windows. However, the importance of organic mixed-valence chemistry should not be seen in terms of the direct applicability of these species but the wealth of knowledge about ET phenomena that has been gained through their study. The great variety of organic redox centers and spacer moieties that may be combined in MV systems as well as the ongoing refinement of ET theories and methods of investigation prompted enormous interest in organic MV compounds in the last decades and show the huge potential of this class of compounds. The goal of this Review is to give an overview of the last decade in organic mixed valence chemistry and to elucidate its impact on modern functional materials chemistry.

Bi(OTf)3 efficiently promotes the reaction to produce a number of cis-substituted dihydropyrans.

Tropylium ion mediated α-cyanation of amines is described. Even in the presence of KCN, tropylium ion is capable of oxidizing various amine substrates, and the resulting iminium ions undergo salt metathesis with cyanide ion to produce aminonitriles. The byproducts of this transformation are simply cycloheptatriene, a volatile hydrocarbon, and water-soluble potassium tetrafluoroborate. Thirteen total substrates are shown for the α-cyanation procedure, including a gram scale synthesis of 17β-cyanosparteine. In addition, a tropylium ion mediated oxidative aza-Cope rearrangement is demonstrated.

The known literature methods to provide access to the title derivatives make use of a base-catalyzed acyl transfer process utilizing either acid halides or anhydrides as acylating agents allowing the synthesis of acylated species in fair to good yields, but none of them is judged satisfactorily to elaborate a library of the title compounds.

The concept of cyclopropenium activation has been extended to include dehydrative rearrangements in the context of the Beckmann rearrangement. Geminal dichlorocyclopropenes are shown to rapidly and efficiently convert oximes to amides at room temperature, with reactivity that far surpasses other organic-based promoters. Twelve total examples are provided, including a complex steroidal substrate on preparative scale. Evidence is provided that suggests previously reported organocatalytic Beckmann rearrangements may in fact be self-propagating rather than catalytic.

A tandem hydrozirconation/Lewis acid mediated cyclization of butenyl substituted oxazolidines allows the synthesis of the target compounds.

Heavy reliance on iterative synthetic strategies represents one of the most serious drawbacks of modern organic synthesis. There has been increasing interest of late in the development of processes that attempt to alleviate this dependence by achieving multiple transformations in a single vessel, thereby circumventing the need for intermittent isolation and purification. One such strategy is encompassed by the term multicatalysis, an approach wherein multiple catalytic reactions are executed in a single flask, either in tandem or sequentially. In this Minireview, some recent efforts in the field of multicatalysis, including our own work, are discussed. In addition, a case regarding the need for consistent terminology in this rapidly developing field is advanced.

The imidazole nucleosides, 4(5)-bromo-5(4)-nitro-1-β-D-ribofuranosylimidazoles, have been prepared via glycosylation of the trimethylsilylated aglycone, 4(5)-bromo-5(4)-nitroimidazole, with tetra-O-acetyl-β-D-ribo-furanose followed by removal of the acetyl protecting groups. The 5-bromo-4-nitro-1-β-D-ribofuranosylimidazole nucleoside was acetonated to produce 5-bromo-4-nitro-1-(2,3-O-isopropylidene-β-D-ribofuranosyl)-imidazole which was cyclized to provide the corresponding anhydronucleoside 5,5′-anhydro-4-nitro-5-oxo-1-(2,3-O-isopropylidene-β-D-ribofuranosyl)imidazole. Sodium hydrosulfide treatment of 5-bromo-4-nitroimidazole nucleoside provided 5-mercapto-4-nitro-1-β-D-ribofuranosylimidazole 5-sodium salt which was alkylated with E-1,5-diiodopent-1-ene to yield 5-(E-1-iodo-1-penten-5-yl)thio-4-nitro-1-β-D-ribofuranosylimidazole. The corresponding iodine-125-labeled compound was prepared similarly using radiolabeled diiodopentene. The 5-bromo-4-nitroimidazole, 5-mercapto-4-nitroimidazole, and 5-iodopentenylthio-4-nitroimidazole nucleosides were cytotoxic to Molt-3 cells in vitro at concentrations higher than 10 μg/mL. The radiolabeled 5-iodopentenylthio-4-nitroimidazole nucleoside showed 2-fold higher uptake in a rapidly growing tumor as compared to uptake in a relatively slower growing tumor in mice.

An X-ray study was performed on single crystals of the compound CeGe 1.6 . The structure is derived from the tetragonal α-ThSi 2 type. The superstructure is shown to be related to the order of vacancies. Magnetic measurements and neutron diffraction experiments showed a ferromagnetic structure with magnetization along the c axis, T C = 6 K and M = 1.5 μ B at T = 1.5 K. The crystal field level scheme is deduced from single-crystal susceptibility and inelastic neutron scattering.

Tri(2-methoxyphenyl)phosphine has been prepared in an excellent yield by metallating methoxybenzene with n-BuLi. TMEDA in hexane and subsequently reacting the resulting lithiomethoxybenzene with phosphorus trichloride in a mixture of THF and hexane.

Regio-as well as stereospecific cis-reductions of a wide variety of acetylenic derivatives can be carried out in absolute ethanol with zinc powder activated with 1,2-dibromoethane and with zinc powder treated successively with dibromoethane and lithium bromocuprate, the first reagent being less powerful and more selective than the second one.

A number of ortho-substituted fluorobenzenes are readily accessible by treating fluorobenzene at -100°C with a 1:1 molar mixture of potassium tert-butoxide and n-butyllithium in tetrahydrofuran and hexane, and subsequently adding an electrophilic reagent.

The structure and methanol synthesis activity of systems derived from binary cerium-silver and ternary cerium-silver-copper intermetallic precursors have been studied in the light of Frost's hypothesis according to which methanol synthesis occurs on a metal-promoted oxide phase. Results were obtained by in situ powder X-ray diffraction (XRD) with concurrent analysis of the exit gas stream by gas chromatography. To attain extensive metal/cerium oxide interaction, activation in N{sub 2}O and CO/H{sub 2}, with and without hydrogen pretreatment, was investigated; pressures up to 50 bar and temperatures up to 500{degree}C were used. No methanol synthesis activity was observed from Ag/CeO{sub 2} systems derived from binary cerium-silver alloys. Furthermore, the activity of the Cu/Ag catalysts derived from the ternary precursor was very significantly reduced relative to that expected by comparison with CeCu{sub 2}-derived catalysts on the basis of its copper content. Thus at least for methanol synthesis catalysts derived from these intermetallic precursors, the identity of the transition metal does indeed appear to be crucial.

Ethereal solutions of 1-lithiocyclohexene and 1-lithiocycloheptene have been prepared from the corresponding chlorocyeloalkenes and lithium chips in the presence of pieces of broken glass.

Trans-chloro-(2-naphthyl)-bis-(triphenylphosphine)nickel has been used to catalyze the conversion of 2-and 3-bromothiophene with alkali cyanide into the corresponding nitriles. A modified procedure for preparing the catalyst is described.

The one-electron oxidised (radical cation) and one-electron reduced (radical anion) forms of the photosensitiser rose bengal have absorption maxima at 470 nm (molar absorption coefficient 21 100 dm3 mol–1 cm–1) and 420 nm (molar absorption coefficient 37 600 dm3 mol–1 cm–1), respectively. The radical anion (RB˙–) undergoes electron-transfer reactions both with oxygen (k= 1.5 × 108 dm3 mol–1 s–1) and diethylenetriaminepentaacetic acid (DTPA)(k= 8.6 × 108 dm3 mol–1 s–1). Rose bengal reacts both with the solvated electron and the semireduced nicotinamide adenine dinucleotide radical (NAD˙) to give RB˙– with second-order rate constants of 3.1 × 1010 and 9.6 × 108 dm3 mol–1 s–1. The one electron-reduction potential E17 for rose bengal, measured via pulse radiolysis, was found to be –511 mV.

Regio- and stereo-controlled syntheses of the title compounds (1) and (2), starting from cyclohexane-1,3-dione (10) and cyclohexa-1,3-diene (17) respectively, are reported.

1,3-Diyne derivatives, (3) and related highly unsaturated compounds have been obtained with excellent overall yields by functionalization of the readily available 1-ethylthio-1,3-butenyne (1) followed by reaction of the derivatives (2) with sodamide in liquid ammonia.

Pure bromopropadiene, BrCH═C═CH2, and the corresponding iodo compound have been obtained with reasonable yields by removing the propargyl halide present in the equilibrium mixtures resulting from treatment of the propargyl halide with CuBr or CuI, with a limited amount of diethylamine.

The enynes HCCCHCHCH 2 R (R  H, Me, OMe, NMe 2 SMe), are converted into dimers by treatment with slightly more than two equivalent of butyllithium. The Z configuration predominates in the dimers obtained after aqueous workup. The lithiated enynes (R  H, Me, SMe) and acetylenic compounds LiCCCH 2 R (R  SMe, C 6 H 5 ) add in an analogous way to the double bond of LiCCCHCH 2 .

The response of ternary SiO 2 -supported Ru/TiO 2 catalysts to a series of characteristic treatments has been examined in detail by chemisorption measurements, XPS, SIMS, and HREM observations, appropriate comparisons being made with binary Ru/SiO 2 and Ru/TiO 2 reference samples. The SMSI state is shown to be air-sensitive and the active highly dispersed phases on the ternary TiO 2 / Ru/SiO 2 catalysts exhibit SMSI behavior even after low-temperature reduction. SIMS and XPS data indicate that the SMSI condition does not involve intermixing of the Ru and TiO 2 phases. Rather it is associated with highly dispersed metal entities whose XP spectra exhibit significant surface core-level binding energy shifts. Further aspects of the SMSI state are also discussed.

The reaction of 1-lithio-1-alkynes with oxiranes under the catalytic action of trimethylgallium afforded the corresponding β-hydroxy acetylenic compounds in good yields with excellent regioselectivities. No isomerization of oxiranes was observed during the reactions because of low Lewis acidity of trimethylgallium. The mechanism including activation of an oxirane by the coordination to trimethylgallium was proposed.