Stereoselective total syntheses of (+)-exo- and (−)-exo-brevicomins, (+)-endo- and (−)-endo-brevicomins, (+)- and (−)-cardiobutanolides, (+)-goniofufurone

Stereoselective total syntheses of aggregation pheromones (+)-exo-brevicomin (9a), (−)-exo-brevicomin (9b), (+)-endo-brevicomin (9c), (−)-endo-brevicomin (9d) and styryllactones (+)-cardiobutanolide (14a), (−)-cardiobutanolide (14b), and (+)-goniofufurone (19a) were achieved in good yields from enantiomerically pure highly functionalized furanoid glycal building blocks (1a-d) involving similar synthetic strategies, thus making these furanoid glycals highly useful building blocks in diversity-oriented synthesis (DOS).     

Molecular Self‐Assembly of Multifunctional Nanoparticle Composites with Arbitrary Shapes and Functions: Challenges and Strategies

The assembly of nanoparticles into complicated, anisotropic shapes has much promise for advanced materials and devices. Developing effective and efficient anisotropic mono‐functionalization strategies is an imperative step in realizing this potential. By functionalizing DNA one at a time to the nanoparticle, a DNA‐nanoparticle building block could have distinct DNA sequences at different locations on the surface of the particle. Since this technology could incorporate nanoparticles of different composition, generating toolboxes of various nanoparticle building blocks (“nano‐toolboxes”) with DNA at defined locations and in defined 3D orientations on a nanoparticle, it promises not only complicated shapes, but also the ability to tune the function of the assembly. The challenges of programmable and scalable multifunctional nanostructure self‐assembly with DNA conjugated to nanoparticles are reviewed. The first difficulty is to control the assembly process so that designed products are formed, and unwanted products are minimized. The design problem for nanostructure construction is both physically and computationally complex. Thus, the other major challenge is to devise design methodologies that move nanostructure construction from trial and error to principled approaches. Strategies to overcome these challenges are also presented by realizing greater control over the final shapes and functions of the self‐assembled nanostructures. Finally, the future perspectives of nano‐toolboxes and their promise in applications such as multifunctional, multicolor, and multimodal contrast nanoagents for medical therapy and diagnostics (theranostics) are described.     

Etching technique study for POF coupler fabrication using circular blocks

A method for developing polymer optical fiber (POF) directional coupler is introduced where the initial procedure is explained. The procedure of fabrication includes using chemical solvent to remove the cladding and exposed the core in order to align the unclad center of the fiber with another similar fiber to develop the coupler. Several experiments using different radii of circular blocks attached with the etched fibers are demonstrated to investigate the output power and losses of the developed coupler in order to build an efficient yet low-cost device. Instead of relying only on silica or glass fiber, POF now can be used as an alternative to improve the network performance in short distance communication system. The measurement parameters laid out offer great outcomes, however, the couplers intended to develop is yet to be realized where deeper research and various experiments are needed in order to develop a simple but optimum performance coupler that can be used for various applications.     

局域网中网络拥塞的成因分析及改进策略

局域网中网络拥塞问题对于大规模的上机考试来说是十分严重的，发生的可能性也比较大，涉及的环节多，原因复杂，加上条件限制，分析处理有一定难度。针对上机考试中的网络拥塞现象进行了分析，并提出了改进策略。     

Transversal Heteroclinic Bifurcation in Hybrid Systems with Application to Linked Rocking Blocks

In this paper, we study heteroclinic bifurcation and the appearance of chaos in time-perturbed piecewise smooth hybrid systems with discontinuities on finitely many switching manifolds. The unperturbed system has a heteroclinic orbit connecting hyperbolic saddles of the unperturbed system that crosses every switching manifold transversally, possibly multiple times. By applying a functional analytical method, we obtain a set of Melnikov functions whose zeros correspond to the occurrence of chaos of the system. As an application, we present an example of quasiperiodically excited piecewise smooth system with impacts formed by two linked rocking blocks.     

Coordination‐driven self‐assembly of Cp*Rh‐Based Rectangles,Cages and Their Host−Guest Binding Study

Supramolecular coordination‐driven self‐assembly rectangle 1a have be formation of distorted shapes, with a strong π···π interactions between the L1 and anthracene in 1b ( 1a  ? anthracene) that changed the size to desired and supported by single‐crystal Xray diffraction data. The formation of 1c( 1a  ? DMF) has been further corroborated by the single‐crystal and 1b also can reaction with decaborane to form ortho‐carborane complex 1d . A self‐assembled triangular prism cage 2a consisting of binuclear half‐sandwich metal precursors [Cp^*₂Rh₂(μ‐BiBzIm)]Cl₂ (BiBzIm = 2,2′‐bisbenzimidazole) ligands and L2 were found to capsulated a triphenylene in cage. Another two kinds of prismatic cages ( 3a and 3b ) were obtained from the reactions of the bis‐chelating‐coordinated [Cp^*₂Rh₂(μ‐CA)]Cl₂(CA = chloranilate) with L2 and L3 in the presence of AgOTf (OTf = CF₃SO₃) in CH₃OH, and cage 3b have a perfect sized cavity to self‐assembled with anthracene in it.     

Aldo‐X Bifunctional Building Blocks for the Synthesis of Heterocycles

Compounds containing oxygen, nitrogen, or sulfur atoms inside the rings are attracting much attention and interest due to their biological importance. In recent years, several methods for the synthesis of such molecules have been reported by using aldo‐X bifunctional building blocks (AXB3 s) as substrates; these are a wide class of organic molecules that contain at least two reactive sites, among them, one aldehyde, acetal, or semiacetal group was involved. Because of the multiple reactivities, AXB3 s are widely used in the one‐pot synthesis of biologically important heterocycles. This review summarizes the synthesis of important heterocycles by using AXB3 s as pivotal components in establishing multicomponent reactions, tandem reactions, and so forth. In many cases, the established reaction systems with AXB3 s were characterized by some green properties, such as easy access to the substrate, mild and environmentally benign conditions, and wide scope of the substrate.     

Hydrogenation of Borylated Arenes

A cis‐selective hydrogenation of abundant aryl boronic acids and their derivatives catalyzed by rhodium cyclic (alkyl)(amino)carbene (Rh–CAAC) is reported. The reaction tolerates a variety of boron‐protecting groups and provides direct access to a broad scope of saturated, borylated carbo‐ and heterocycles with various functional groups. The transformation is strategically important because the versatile saturated boronate products are difficult to prepare by other methods. The utility of the saturated cyclic building blocks was demonstrated by post‐functionalization of the boron group.     

Dihalomethanes as Bent Bifunctional XB/XB‐Donating Building Blocks for Construction of Metal‐involving Halogen Bonded Hexagons

The dihalomethanes CH₂X₂ (X=Cl, Br, I) were co‐crystallized with the isocyanide complexes trans‐[MX^M₂(CNC₆H₄‐4‐X^C)₂] (M=Pd, Pt; X^M=Br, I; X^C=F, Cl, Br) to give an extended series comprising 15 X‐ray structures of isostructural adducts featuring 1D metal‐involving hexagon‐like arrays. In these structures, CH₂X₂ behave as bent bifunctional XB/XB‐donating building blocks, whereas trans‐[MX^M₂(CNC₆H₄‐4‐X^C)₂] act as a linear XB/XB acceptors. Results of DFT calculations indicate that all XCH₂–X???X^M–M contacts are typical noncovalent interactions with estimated strengths in the range of 1.3–3.2 kcal mol^?1. A CCDC search reveals that hexagon‐like arrays are rather common but previously overlooked structural motives for adducts of trans‐bis(halide) complexes and halomethanes.