A three-dimensional covalent organic framework (COF-505) constructed from helical organic threads, designed to be mutually weaving at regular intervals, has been synthesized by imine condensation reactions of aldehyde functionalized copper(I)-bisphenanthroline tetrafluoroborate, Cu(PDB)2(BF4), and benzidine (BZ). The copper centers are topologically independent of the weaving within the COF structure and serve as templates for bringing the threads into a woven pattern rather than the more commonly observed parallel arrangement. The copper(I) ions can be reversibly removed and added without loss of the COF structure, for which a tenfold increase in elasticity accompanies its demetalation. The threads in COF-505 have many degrees of freedom for enormous deviations to take place between them, throughout the material, without undoing the weaving of the overall structure.

Carbohydrates and natural products serve essential roles in nature, and also provide core scaffolds for pharmaceutical agents and vaccines. However, the inherent complexity of these molecules imposes significant synthetic hurdles for their selective functionalization and derivatization. Nature has in part addressed these issues by employing enzymes that are able to orient and activate substrates within a chiral pocket, which dramatically increases both the rate and selectivity of organic transformations. In this article we show that similar proximity effects can be utilized in the context of synthetic catalysts to achieve general and predictable site-selective functionalization of complex molecules. Unlike enzymes, our catalysts apply a single reversible covalent bond to recognize and bind to specific functional group displays within substrates. By combining this unique binding selectivity and asymmetric catalysis, we are able to modify the less reactive axial positions within monosaccharides and natural products.

Unveiling the physical mechanisms of high performance in potassium sodium niobate-based ceramics from diffused multi-phase coexistence and a single domain feature.

All in together: The title reaction takes place under mild conditions in the presence of a chiral phosphonic acid catalyst to provide 4‐aryl substituted 1,4‐dihydropyridines with up to 98 % ee (see scheme). The products are useful substrates for the asymmetric synthesis of tetrahydropyridines and multifunctional piperidines, which are common substructures of natural products and pharmaceuticals. R1=aryl; R2,R3=alkyl.

Ex‐changing places: A highly enantioselective desymmetrization of 1,2‐diols has been developed in which the catalyst utilizes reversible covalent bonding to the substrate to achieve both high selectivity and rate acceleration (see scheme, PMP=pentalmethylpiperidine, TBS=tert‐butyldimethylsilyl). Induced intramolecularity is responsible for the enhanced rate, thus allowing the reaction to be performed at room temperature.

Through introducing the iPP fibers having different molecular weights into their supercooled or molten matrices, fiber/matrix single polymer composites of iPP have been prepared, and the obtained interfacial morphologies were studied by means of polarized light microscopy. It was found that the interfacial supramolecular structure was affected by not only the introduction temperature but also the molecular weight of the iPP fibers. At low fiber introduction temperatures, solid iPP fiber induces the growth of R-iPP crystals and results in the formation of pure R-iPP transcrystallization layer in the vicinity of iPP fiber regardless of its molecular weight. At high fiber introduction temperatures, completely molten iPP fiber, with either high or low molecular weight, loses its nucleation ability toward iPP matrix. The interfacial structure induced by incomplete molten iPP fibers is different from fiber to fiber. This has been explained in terms of different relaxation behavior of the fiber, which has been further confirmed by the annealing experiment of the high molecular weight fiber/matrix system at the fiber introduction temperature. † Ph. D. candidate of the Chinese Academy of Sciences.

This paper demonstrates that the secondary hydroxyl can be functionalized in preference to the primary hydroxyl of a 1,2-diol. The site selectivity is achieved by using an enantioselective organic catalyst that is able to reversibly and covalently bond to the diol. The reaction was parlayed into a divergent kinetic resolution on a racemic mixture, providing access to highly enantioenriched secondary protected 1,2-diols in a single synthetic step.

The application of hydroformylation to the synthesis of quaternary carbon centers is reported. The synthesis of the highly substituted carbon is achieved by applying a catalytic amount of 1. Ligand 1 serves as a catalytic directing group by covalently and reversibly binding to both the substrate and catalyst. The intramolecular nature of the directing group strategy accelerates the hydroformylation reaction such that the reaction is performed at mild temperatures (35–55 °C) and with excellent regioselectivity (b:l > 94:6).