Constructing α‐stereogenic amides and ketones : The highly regioselective and enantioselective conjugate addition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).
Caught on the hop : In multistep electron transfer (ET) reactions through peptides, aliphatic amino acids can also act as relay stations. With cysteine, the reaction occurs as a proton‐coupled electron transfer (PCET) with water used as a mediator for the proton transfer (see picture).
A novel sialon phosphor is characterized by an unusual silicate framework, built up of edge‐ and vertex‐sharing tetrahedra (orange and green). Owing to pronounced pseudotranslations, the compound is highly disordered. It was investigated in detail by X‐ray diffraction and electron microscopy. Despite the disorder, all Sr atoms (yellow spheres) exhibit very similar coordination spheres, and doping with Eu2+ results in efficient green luminescence (see inset; Em.=emission, Exc.=excitation, Refl.=reflection).
Economical approach : The first organocatalytic asymmetric intramolecular hydroarylation of phenol‐ and aniline‐derived enals offers one of the most straightforward and atom‐economic approaches to enantioriched chromans and tetrahydroquinolines (up to 96 % ee; see scheme).
Carbon‐rich‐quick scheme : A carbon‐rich solid product made up of uniform micrometer‐sized spheres of tunable diameter has been synthesized by the hydrothermal carbonization of saccharides. These microspheres possess a core–shell chemical structure based on the different nature of the oxygen functionalities between the core and the outer layer (see figure).
Dynamic duo : Magnetic resonance imaging (MRI) can visualize deep regions of living bodies, whereas fluorescence measurement offers excellent sensitivity. These methods thus offer signal enhancement potential for detecting enzyme activities. A dual‐mode off/on probe to detect caspase‐3 activity by fluorescence and 19F MRI is presented.
Branching out : The mobility of linear polymers changes upon branching, which has a pronounced effect on processability and drawability. Regularly branched model polyolefins were studied by advanced solid‐state NMR spectroscopy, and twist defects around the branches in the crystalline regions are identified. For lower branch content, the twisting motions are decoupled; for higher content, collective motion is found (see picture).
Dynamic surfaces : The conformational transition of 2,6‐bis(1‐aryl‐1,2,3‐triazol‐4‐yl)pyridine (BTP) derivatives, triggered by a change in pH, has been observed with a sub‐nm resolution by STM at the solid–liquid interface. Upon addition of trifluoroacetic acid two different BTP molecules, each forming a highly ordered physisorbed monolayer, underwent significant conformational changes from their “rosette” to their “tetragon” forms, as reflected in dramatically altered 2D self‐assembly over large areas extending over hundreds of nanometers (see graphic).
Block copolymers in seconds : Catalyst‐free, ambient‐temperature click conjugation of individual polymer strands becomes possible using novel ATRP‐derived cyclopentadienyl‐capped polymers in an extremely rapid hetero‐Diels–Alder cycloaddition with macromolecules equipped with electron‐deficient dithioester end groups prepared by the RAFT process.
′I′ is all the hype : A twofold excess of iodoarene in the title reaction leads to ortho‐quinols in good yields, whereas organocatalytic versions of this reaction enable subsequent epoxidation in a regio‐ and diastereoselective fashion. Chiral iodobiarenes led to enantioselectivities up to 50 % ee. m‐CPBA=meta‐chloroperoxybenzoic acid.
Special agents for protein capture : Iterative in situ click chemistry (see scheme for the tertiary ligand screen) and the one‐bead–one‐compound method for the creation of a peptide library enable the fragment‐based assembly of selective high‐affinity protein‐capture agents. The resulting ligands are water‐soluble and stable chemically, biochemically, and thermally. They can be produced in gram quantities through copper(I)‐catalyzed cycloaddition.
Seeing the light : An electrode is assembled by linking acid‐shortened single‐walled carbon nanotubes with carboxylic groups to a gold surface modified with a cysteamine monolayer. The electrode generates a photocurrent when illuminated with visible light in the presence of an electroactive species (see picture). With an appropriate applied potential the device behaves as a photodiode.
At first sight , carbon nanotubes seem to be perfect materials, but appearances can be deceptive. Carbon nanotubes contain impurities and these impurities are often contaminated by yet other impurities. Interestingly, while main impurities (such as Co and Mo) are not electrochemically active, impurities of impurities (such as Fe in this case) dominate the electrochemistry of carbon nanotubes for reduction of important biomarkers, such as hydrogen peroxide. H. Iwai and M. Pumera discuss the importance of this observation in their Full Paper on page 554 ff.
State‐of‐the‐art molecular‐beam techniques reveal that the lowest lying electronic excited state in purine is the nπ* state. Using multiphoton ionization spectroscopy, the origin is found to occur at 31 309 cm?1, and a vibrational structure is visible that is assigned to the skeletal motion of the ring (see figure).
Cross‐coupling carbenes : The coupling of a propargylic ester with a diazoalkane in the presence of [RuCl(cod)Cp*] catalyst leads to the formation of functionalized conjugated dienes with high stereoselectivity. The reaction involves the cross‐coupling of a vinylcarbene fragment, arising from a ruthenium‐catalyzed propargylic ester rearrangement, with a diazoalkane carbene.
The combination of imidazolium surfactants with α‐cyclodextrins (CDs, in green) was used as a control element in the thermoregulated aqueous olefin hydroformylation. The self‐assembly of the imidazolium surfactants (red) favors the micellization process at high temperatures, whereas at lower temperatures the complexation of the surfactant monomers into the α‐CDs is favored.
