Chemistry - A European Journal

Endohedral fullerene dyads… are described by L. Echegoyen et al. on page 864 ff., which have been obtained by pyrrolidine and cyclopropane derivatives of the trimetallic nitride templated (TNT) endohedral metallofullerenes I_h-Sc₃N@C₈₀ and I_h-Y₃N@C₈₀ connected to an electron-donor unit (i.e., tetrathiafulvalene, phthalocyanine or ferrocene) through 1,3-dipolar cycloaddition reactions of azomethine ylides and Bingel–Hirsch-type reactions.

Broadening the horizon: Based on the well-known Meerwein arylation, in which an aryl and a halogen substituent are coupled to an olefinic substrate, new reaction types have been developed that allow the introduction of a broad spectrum of other atoms (see scheme) and functional groups at the place of the original halogen and which are applicable to a wide range of olefinic substrates.

Go catalyst go! Highly dispersed 10 % Pd/HP20 was readily prepared from Pd(OAc)₂ and a commercial synthetic adsorbent, DIAION HP20. The 10 % Pd/HP20 has a strong catalyst activity and used for the hydrogenation and ligand-free Suzuki–Miyaura coupling reaction (see figure).

Privileged scaffolds: Breaking the symmetry of 1,4-diyne scaffolds by nucleophilic amine addition onto one of two equivalent alkynoate units affords chain-functionalized tetrasubstituted pyrroles with five points of functional diversity and two points for complexity generation. The domino reaction manifold entails an aza-Michael addition, a 5-endo-digonal cyclization, and a [3,3]-sigmatropic rearrangement.

From five to two: The addition of deprotonated Strecker products to N-acylimines permits the synthesis of tetrasubstituted imidazoles or trisubstituted oxazoles in three or four steps, respectively. In total, the target compounds are prepared from two aldehydes, a primary amine, an acid chloride and ammonia (see scheme).

Controlled abstraction: [Ph₃C][B(C₆F₅)₄] is best known for its excellent ability to abstract alkyl ligands, however, the present study on mono(indenyl)–Sc–dialkyl/[Ph₃C][B(C₆F₅)₄] systems has found that [Ph₃C][B(C₆F₅)₄] can abstract a π-bonded indenyl ligand rather than a σ-alkyl ligand (see scheme). The abstraction pathway can be controlled by changing the substituents on the indenyl ligands.

Donation is not from an sp³orbital: Decomposition analysis, based on absolutely localized molecular orbitals, provides an alternative and somewhat unconventional view of hydrogen bonding in the water dimer. A new description of the electron-donating orbital is uncovered: unlike sp³ lone pairs, a single donor–acceptor orbital pair forms, in which the donating orbital changes its orientation according to the relative positions of the two molecules.

Temperature sensitive: The reaction of a manganate mixture of butylsodium, bis(trimethylsilyl)manganese and diisopropylamide in a 1:1:3 stoichiometric ratio with ferrocene yields a novel hydrido inverse crown (shown in figure) at high temperature, and a trimanganese trinuclear ferrocenophane at lower temperatures.

Endohedral fullerene dyads: The reactivity of I_h-Sc₃N@C₈₀ and I_h-Y₃N@C₈₀ (see figure) towards 1,3-dipolar azomethine ylide and Bingel–Hirsch cycloaddition reactions was explored in order to construct different electron donor–acceptor conjugates. The unique redox properties of the structures formed were investigated by means of cyclic voltammetry and the experimental results were supported by density functional calculations.

Color tuning! By using the imide group of perylene monoimides as an acceptor and selectively functionalizing the 1-, 6- and 9-positions with different electronic substituents, we have constructed a “push–pull”-type family of perylenes, exhibiting a rainbow of colors, tunable spectroscopic and electrochemical properties.

Cell imaging: Introduction of pyridine units in the core of ditopic nonadentate ligands based on bis(benzimidazole)pyridine moieties results in a europium bimetallic helicate [Eu₂(L^C5)₃] which can be excited up to 405 nm and therefore act as a lanthanide luminescent bioprobe for cell imaging under confocal microscope (see graphic).

Dyeing to bind: The interactions between the crystal violet (CV) dye and G-quadruplex, duplex, or single-stranded DNAs were studied. Good discrimination between quadruplexes and duplex or single-stranded DNAs was achieved with the fluorescence or energy-transfer fluorescence spectra of CV (see graph). The binding-stoichiometry ratio of CV to G-quadruplexes and the fraction of G-rich oligonucleotide that engages in G-quadruplex structures in the presence of the complementary sequence can also be easily determined.

Structural confirmation!! Eight years after isolation, and five years after structural revision, the total synthesis of (+)-neomarinone (see scheme) proves its relative and absolute configuration.

More explosive than TNT? High density energetic salts containing nitrogen-rich cations and nitranilic anion (see figure) were readily synthesized. The highly symmetric and oxygen-containing anion makes these compounds have high densities, low water solubilities, and high thermal stabilities (T_d> 200 °C). Theoretical performance calculations indicate their potential applications as energetic materials.

Rigid or flexible? Zincocenes [ZnCp′₂] may adopt different structures depending upon the nature of the cyclopentadienyl substituents. A zincocene with a rigid η⁵/η¹(σ) solution and solid-state structure has been prepared and structurally characterised as containing η⁵-C₅Me₅ and η¹-C₅Me₄SiMe₃ rings (see figure).

An alternative to Si–OH: A straightforward synthetic route to a fully dehydroxylated and clean silicon–hydride modified silica surface is described (²⁹Si NMR chemical shifts are shown). This chlorination/reduction sequence represents an ideal strategy to provide the starting material for further molecular silica surface modifications.

Functionalized carba-closo-dodecaborates: Carba-closo-dodecaborate anions with primary amino substituents bonded to the boron atom in the 2-position: [1-R-2-H₂N-closo-CB₁₁H₁₀]⁻ (R=H, Ph, H₂N, CyHN) have been synthesized and characterized by spectroscopic and structural methods (see picture). The pK_a values of the corresponding protonated carboranes were studied and compared to those of 1-H₃N-closo-CB₁₁H₁₁.

Bond, double bond: A variety of nitrogen-containing cyclic adducts can be produced in moderate to good yields under mild conditions by Lewis acid or Brønsted acid catalyzed reactions of vinylidene cyclopropanes with activated carbon–nitrogen, nitrogen–nitrogen, and iodine–nitrogen double-bond-containing compounds (see scheme; Tf: trifluoromethanesulfonyl; Ts: toluene-4-sulfonyl).

Get catalytic! A general enantioselective synthesis of functionalized nitrocyclopropanes by organocatalytic conjugate addition of a variety of bromonitroalkanes to α,β-unsaturated enone systems is presented. This reaction is catalyzed by cinchona alkaloid 1 (see scheme).

Electrocrystallization afforded a rare example of a mononuclear Mn^III complex that is stabilised solely by neutral N ligands (see picture). Its D value, which is large compared to that of other mononuclear Mn^III complexes, was determined from a combination of magnetic measurements and theoretical calculations; the positive sign is consistent with the compressed octahedral geometry revealed by X-ray crystallography.

You've been framed: In situ conversion from a meso ligand to a racemic ligand by pH control has been realized during the crystallization process of seven Zn-tetrahydrofurantetracarboxylate (L; see scheme) complexes.

Going in a flash! The Mizoroki–Heck synthesis of cinnamic esters by using low levels of Pd catalyst loading can be performed efficiently in a high-temperature/pressure stainless steel flow reactor (X-Cube Flash; see scheme).

The α-effect: Our study on the reactions of O-p-nitrophenyl thionobenzoate (1) with HO⁻, p-ClPhO⁻, and oximate⁻ revealed major differences in the reactivity by changing the electrophilic center from CO (2) to CS (1).

Functionalized organostibine transfer agents, prepared in situ from functionalized azo initiators and tetramethyldistibine, mediate the highly controlled living radical polymerization of vinyl monomers. Selective transformations of the organostibanyl polymer end group afforded homo- and hetero-telechelic polymers (see picture) with defined polymer-end functional groups with controlled molecular weights and molecular weight distributions.

Protection/deprotection for probe design: Based on the concept of functional group protection/deprotection, a fluorescent Cu²⁺ probe was constructed, which showed ratiometric fluorescent response to Cu²⁺ with a large emission wavelength shift and displayed high selectivity for Cu²⁺ over other metal ions due to distinct deprotection conditions (see figure).

Multitasking aptamers at work! Two G-quadruplex aptamers are identified as multifunctional aptamers that can simultaneously bind hemin and a target protein, and their corresponding hemin–DNA complexes reveal excellent peroxidase-like activities. Such multiple functions enable these aptamers to serve as a DNAzyme-based platform for facilely sensing protein ligands with high sensitivity, which is demonstrated by applying AGRO100 to the chemiluminescence detection of cell-surface-expressed nucleolin (see scheme).