Three types of novel radical cyclization of 1,6-enynes with sulfonyl hydrazides have been presented, which provided convenient synthetic approaches for accessing five-membered cyclic lactams, five-membered cyclic lactams containing C–I bond, and six-membered cyclic lactams. Notably, these transformations are implemented in metal-catalyst-free systems, in which three classes of important lactam derivatives were synthesized with selectivity and controllability from the same substrate using water as the green solvent.

Two kinds of polyvinyl chloride (PVC)/organophilic montmorillonite (OMT) nanocomposites are prepared by a melt intercalation method. This study has been designed to determine if the presence of iron and zinc ions in the structure of montmorillonite (MMT) lattice can affect thermal, flame retardant and smoke suppressant properties. The information about the morphological structure of PVC/OMT nanocomposites was obtained using X-ray diffraction and transmission electron microscopy. The thermal and flame retardant properties of the nanocomposites were characterized by thermogravimetric analysis, limiting oxygen index and smoke density. The nanocomposites based on Fe-OMT exhibit better thermal, flame retardant properties and lower degradation degree than those of pure PVC. The degradation mechanism was studied by pyrolysis, gas chromatography and mass spectrometry (Py-GC-MS).

Iron-catalyzed oxidative cyclization of olefinic 1,3-dicarbonyls with ketone C(sp3)–H bonds through C-C and C-O bond formations has been described for the first time. A broad substrate scope and ease of...

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A novel polychloromethylation/acyloxylation of 1,6-enynes with chloroalkanes and diacyl peroxides through dual roles designs to prepare 2-pyrrolidinone derivatives with polychloromethyl units has been developed by the use of inexpensive copper...

For decades, underwater vehicles have been performing underwater operations, which are critical to the development and upgrading of underwater robots. With the advancement of technology, various types of robots have been developed. The underwater robotic snake is a bioinspired addition to the family of underwater robotic vehicles. In this paper, we propose an innovative underwater snake robot actuated by rigid propulsions and soft joints, which can improve the swimming efficiency and flexibility of the robot and reduce the probability of collision leading to damage. Existing math models of robotic snakes typically incorporate only planar motion, rarely considering spatial motion. So, we formulate a complete three-dimensional dynamic model for the robotic snake, which is extended by deriving expressions for the geometric Jacobians. This modeling approach is well suited since it provides compact matrix expressions and easy implementation. We use the constant curvature method to describe the configuration of the soft joint, use the Lagrangian method to obtain its dynamic characteristics, and focus on deriving the visco-hyperelastic mechanical energy of the soft material. Next, the local dynamics of soft members are extended as a nonholonomic constraint form for modeling the snake robot. Finally, the multi-modal swimming behavior of the robot has been verified by simulations, including forward and backward rectilinear motion, yaw turning, pitch motion, and spiral rising motion. The overall results demonstrate the effectiveness and the versatility of the developed dynamic model in the prediction of the robot trajectory, position, orientation, and velocity.

A novel method for assembling pyrrolidine-2,4-diones from 1,5-enenitriles and acetone/acetonitrile via a cyclization/hydrolysis has been established under metal catalyst- and base-free conditions, with Oxone as a green oxidant and H2O as an additive at 90-110 ℃. This strategy is highlighted by cyclization/hydrolysis of alkyl cyanides, achieving direct C(sp3)–H oxidative functionalization, and giving full conversion of the substrates with excellent functional group compatibility.

The simple and convenient metallic mask method is a significant method of preparing diamond nanostructures. The metallic mask method has poor repeatability and can not give the ideal results, because it is supported by no theory about formation of surface mental nanoparticles and its technological parameters are optimized by no experimental techniques that are expensive either. Aiming at the formation and performance of the diamond/Al interface, this paper adopts the first-principles to study the adsorption and migration behavior of Al atoms on the H-terminated diamond surface and the structure of the diamond/Al interface. The results show that the highest adsorption energy is at the T4 position, which is only 0.181 eV, through comparing the adsorption energies of Al atoms at the highly symmetrical positions (Top, Br, H3 and T4) on the surface of the H-terminated diamond (111). The adsorption energies at these different positions are similar and the maximum difference is only 0.019 eV. There is formed no chemical bond, although Al has partial charge transfer on the H-terminated surface through the analysis of differential charge density and worse layout distribution. This phenomenon can be considered as electrostatic adsorption. That is to say, the adsorption of Al atoms are physical adsorption. The smooth potential energy surface also makes it easier for Al atoms to migrate on the diamond surface. The calculation results reveal that the migration activation energies of the two possible migration paths (from T4 position to Br position and from T4 to Top position) are 0.011 eV and 0.026 eV respectively. The above results imply that the metal Al and diamond are mainly connected by weak force, so the adhesion work of the three diamond/Al interface structures is compared based on the geometric stacking structure. The results show that the adhesion work of the three interfaces is around 0. These results indicate that the stability of the diamond/Al interface is not high and the stable structure of the interface is easily destroyed when the external environment changes. This speculation can be confirmed in molecular dynamics. When the simulated temperature is 300 ℃, the liquefied metal Al obviously accumulates into spheres. According to the above research results, we deduce that the metallic mask method does not require high requirements for the relationship between the metal and the substrate material, which depends mainly on the surface topography of the base material. This research provides an important theoretical reference for understanding the formation mechanism of metal nanomasks.