Chemistry - A European Journal

In contrast to nucleophilic fluorodesilylation involving the formation of a Si−F bond, the electrophilic fluorodesilylation of silanes and silyl enol ether derivatives allows the preparation of a wide variety of fluorine-containing compounds (see scheme).

A first insight into the magnetic interaction between a 5f element and a 3d transition metal in a molecular compound was possible with a novel class of complexes, in which the central U^IV ion is associated with two M^II ions by means of a hexadentate Schiff base ligand (see figure). The comparative study of the Cu₂U, Zn₂U, Cu₂Zr, and Cu₂Th compounds revealed that the Cu²⁺ and U⁴⁺ ions are ferromagnetically coupled.

The oxidation of extended TTF (tetrathiafulvalene) oligomers (see scheme) and the X-ray structures of new cation radical salts are described. The effects of the structure to orient the cation radical towards a π-dimerization or a disproportionation reaction are described.

Predictable target macrocycles can be made from a virtual combinatorial library (VCL) derived from diamines and pyridine dialdehydes by addition of alkaline earth ions of different sizes, as per the scheme.

4-(Trifluoromethoxy)anisole is deprotonated ortho to the OCH₃group rather than ortho to the strongly electron-withdrawing CF₃O group. The trifluoromethoxy group can exert a long-range effect, as shown here, that considerably lowers the basicity of arylmetal compounds even when it is located in a remote position. The structure and distance dependence of substituent effects can be rationalized by assuming superposing σ- and π-polarizing interactions.

Hydrogenation in a stepwise manner: Alkylidyne moieties on the organometallic oxide [Ti₃CpO₃] are hydrogenated under mild reaction conditions in a stepwise manner with different organic amines by formation of alkylidene, alkyl, and alkane groups. In some cases, thermal dehydrogenation of the μ-alkylidene groups has been observed to give the starting μ₃-alkylidyne compounds.

Cyclodextrins are ideal scaffolds for the attachment of bioactive molecules such as glycosides (see scheme). We describe herein a study on both the inclusion complexation behaviour and lectin binding affinity of branched and hyperbranched β-cyclodextrins.

High specific rotation without a chromophore—this remarkable behavior was observed for (M)-(−)- and (P)-(+)-trispiro[2.0.0.2.1.1]nonanes [(M)- and (P)-3] as well as (M)-(−)- and (P)-(+)-tetraspiro[2.0.0.0.2.1.1.1]undecanes [(M)- and (P)-4]. These enantiomerically pure unbranched [4]- and [5]triangulanes show helical arrangement of σ bonds, as confirmed by a full valence space single excitation configuration interaction treatment (SCI) and DFT computations.

The highly flexible synthesis of the new family of ferrocenyl phosphane ligands 1 offers many possibilities for variation of their substituents. The structure of 1 can thus be rapidly modified to optimize ligand–substrate matching. Ligands 1 give excellent enantioselectivities in the metal-catalyzed hydrogenation of functionalized C=C, C=O, and C=N bonds and 1,3-dicarbonyl compounds. Furthermore, both configurations of the reduction products could be obtained by merely modifying the substituent in the position α to the ferrocene moiety.

The powerful musk odorant (S,S)-(−)-Vulcanolide can be synthesized by enantioselective protonations (EP) of selected enolates (see scheme). Two efficient enantioselective syntheses of the more active (S,S)-enantiomer of the title compound are described. A third EP was applied for the determination of the absolute configuration of vulcanolide.

The stabilization by formylamino side chain and solvent effects together with the inductive effect of the SO₃ group and its active role as a hydrogen shuttle determine the mechanism of the water-assisted alkaline hydrolysis of 3-formylamino-2-azetidine-1-sulfonate ion (see figure) allowing thus to theoretically rationalize experimental data.

A new interpretation for the indenyl effect, which is based on based on the stability of both the η⁵ reactants and the η³ intermediates (see plot) is derived from a density funtional theory/B3LYP study of the two-electron reduction of [(η⁵-Cp′)(η⁵-Cp)Mo(CO)₂]²⁺ (Cp′ = Cp, Ind).

Three-dimensional superlattices can be formed from bundles of molecular dumbbells. These dumbbells, which consist of a conjugated-biphenyl rod segment and aliphatic polyether dendritic wedges with different cross-sections, were synthesized and characterized, and their self-assembling behavior was investigated. X-ray diffraction and density measurements showed that with increasing cross-section of the dendritic wedge, the number of molecules per aggregate decreases, and, as a consequence, the rod-bundle cross-section decreases.

A suitable position for a homochiral p-tolylsulfinyl group of an alkene allows for its diasteroselective intramolecular thermal [5C+2C] cycloaddition to β-silyloxy-γ-pyrones. Switching from the sulfinyl to a sulfonimidoyl group allows one to reverse the sense of the diastereofacial selectivity. The resulting oxa-bridged cycloadducts can be readily elaborated into enantiopure, highly functionalized tetrahydrofurans and seven-membered carbocyclic derivatives as shown.

In order to decipher the anchor dependency in liposomal gene delivery fifteen structural amphiphiles of Series 1 and 2 have been synthesized. These novel non-glycerol based simple monocaionic transfection lipids were then subjected to detailed structure–activity, physicochemical and biophysical investigations.

An efficient and highly versatile stereocontrolled synthesis of functionalized, angularly fused tricyclic ring systems 4 from readily available (1-alkynyl)carbene complexes (OC)₅M=C(OEt)C≡CR (M = Cr, W; R = Ph, c-C₆H₉) involves the formation of a 1-metalla-1,3,5-hexatriene from the (1-alkynyl)carbene tungsten complex (OC)₅W=C(OEt)C≡Cc-C₆H₉ (1), and its thermally induced π-cyclization to a tetrahydroindene, which then reacts with a pyran-2-ylidene complex 3 (M = Cr, W).

Very good regio- and stereoselectivities were observed in the new cyclization of dilithiated cycloalkanone derivatives with 1,4-dibromo-2-butene which results in formation of 2-vinyl-hexahydro-2,3-benzofurans. These products were efficiently transformed into functionalized bicyclo[3.2.1]octan-8-ones by a new palladium-catalyzed rearrangement reaction as shown. The bicyclo[3.2.1]octane skeleton is present in a number of pharmacologically important natural products.

A novel self-assemling supermolecule was formed in aqueous solution at neutral pH. Its truncated tetrahedral interior can encapsulate a hydrophobic guest molecule such as adamantane (depicted here).

Water/bromine mixtures occupy an important place in chemistry. What is the nature of the complex formed in the initial interaction of water and dibromine? This interesting species has been identified in the gas phase by observing its rotational spectrum, thereby allowing its geometry and binding strength, as well as the extent of electronic transfer (both from H₂O to Br₂ and within Br₂) on complex formation, to be established. The potential governing inversion of the confuguration at O has been determined from ab initio calculations.

Bis(terpyridine)-type ligands yield well-organised structures (see picture) upon adsorption on highly ordered pyrolytic graphite (HOPG) due to weak inter- and intramolecular hydrogen bonds. Coordination of Co^II and Zn^II ions afford tetranuclear [2×2] grid-like complexes. The Co complex forms a less stable but still well-organised array on HOPG.

The unique [(RS)₂Fe(CN)₂(CO)] unit found in the active centers of [NiFe] hydrogenases could be modeled by the title complex. The [Fe(CN)₂(CO)(′S₃′)]²⁻ ion (see scheme) forms diastereoselectively from [Fe(CO)₂(′S₃′)]₂ and CN⁻. It could be completely characterized, is redox active, and exhibits ν(CO) and ν(CN) frequencies that are strongly shifted in protic solvents. The ν(CO) shifts are larger than any ν(CO) shift observed for [NiFe] hydrogenases in most different redox states.

The kinetics and the products of the bromination of several cyclic allenes (1 a–e) have been investigated in 1,2-dichloroethane and methanol. The relationship between steric strain and reactivity has been discussed in the light of the mechanisms more recently proposed for Br₂ and Br₃⁻ addition to double and triple bonds. Theoretical calculations have been also carried out to support the conclusions.

The design of a hexakisadduct containing six o-phenylenediamine addends (see figure) is based on the fact that a sixfold addition of malonates by a template mediation technique leads to adducts with a pseudo-octahedral T_h-symmetrical addition pattern in good yields and regioselectivities. This approach requires the symmetrical incorporation of the o-phenylenediamine moiety into a cyclic malonate.