Programmable organic light‐emitting diodes: UV irradiation converts an oxetane‐functionalized dithienylethene derivative from its colorless open form into a dark blue closed form, while visible light reverses the reaction. In the Communication on page 4038 ff., K. Meerholz and co‐workers describe a reversibly switchable organic light‐emitting diode based on this principle.
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.
The novel Yb succinate metal–organic framework exhibits a reversible single‐crystal to single‐crystal polymorphic transformation (see figure) when it is heated above 130 °C, returning to its initial form when back at room temperature. This transformation produces a change in the coordination sphere of the Yb atoms, which influences the catalytic activity of the material.
No hurdle is too high : The regioselectivity and stereoselectivity of the halohydroxylation of non‐activated allenes are controlled by a remote sulfinyl group through anchimeric assistance (see scheme). The resulting halohydrines are excellent chiral targets for the preparation of optically pure propargylic alcohols and Baylis–Hillman‐type products.
Paddle wheels and pillars : Layered 3D metal–organic frameworks comprised of paddle‐wheel coordination units are constructed under a variety of conditions to incorporate bridging ligands (as illustrated) that impart desired properties, such as guest‐exchange behavior, luminescence, microporosity, and stability, to the material.
Optically active tertiary amines are readily prepared by iridium‐catalyzed asymmetric hydrogenation of unfunctionalized enamines (see scheme). The best enantioselectivities with >90 % ee were obtained with N‐aryl‐ and N‐benzyl‐substituted enamines with a terminal double bond. The hydrogenation of enamines derived from cyclic ketones, which has not been reported yet with other catalysts, gave enantiomeric excesses of up to 87 %.
Amino sulfonamide catalyst : A distal proton of the axially chiral amino sulfonamide (S)‐ 1 realized the opposite diastereoselectivity in Mannich and cross‐aldol reactions compared with that observed in proline‐catalyzed reactions. The reactions catalyzed by (S)‐ 1 proceeded smoothly to give the anti‐Mannich and syn‐aldol adducts in excellent enantioselectivity (see scheme).
X‐ray vision : Single‐crystal XRD experiments (see picture) reveal the excited‐state structure of the photomagnetic heterobimetallic title complex. The system shows a decrease in all the iron–ligand bond lengths, suggesting that photoexcitation involves a ligand‐to‐metal charge transfer or a change in the superexchange coupling between the metal centers.
Co(OH) 2 that blooms : Flowerlike hollow spherical architectures of cobalt hydroxide obtained through a facile solvothermal process are reported for the first time (see picture). Their growth process involves aggregation of cobalt hydroxide nanoparticles into solid spheres and a hollowing effect through subsequent dissolution‐diffusion‐redeposition of the smaller crystallites under the surface layer.
Tackling blocks : The isoprene‐assisted radical coupling (I‐ARC) of polymers prepared by cobalt‐mediated radical polymerization (see picture) is the first efficient radical coupling method that is not restricted to short chains. When applied to AB diblock copolymers, I‐ARC constitutes a straightforward approach to the preparation of novel symmetrical ABA triblock copolymers.
Lighting up : A G‐quadruplex‐specific fluorescent probe was designed combining the specificity of the pyridodicarboxamide motif for guanine quadruplexes and the fluorescence properties of thiazole orange. While the assembly of the two partners through a flexible linker leads to a nonselective probe, merging them in a single, rigid scaffold leads to a dye that elicits the properties required for G‐quadruplex sensing.
Molecular Lego : Polyketides represent a highly diverse group of natural products with structurally intriguing carbon skeletons (see picture) which are assembled from simple acyl building blocks. A combination of chemical, biochemical, and genetics studies have provided exciting new insights into the programming of polyketide assembly and the sophisticated enzymatic machineries involved. This review highlights recent developments in the field.
Economic and practical advantages are offered by the iron(III)‐catalyzed and air‐mediated tandem coupling/hydroarylation/dehydrogenation of simple readily available aldehydes, alkynes, and amines for the synthesis of 2, 4‐disubstituted quinolines (see scheme).
