Organocatalytic enantioselective synthesis of double S-shaped quadruple helicene-like molecules.

Helicene-shaped molecules are compelling chemical structures with unique twisted helical chirality and remarkable properties. Although progress occurs in the catalytic asymmetric synthesis of helicene (-like) molecules, the enantioselective synthesis of multiple helicenes, especially four or higher helicity, is still challenging and has yet to be achieved. Herein, we report an organocatalytic [4 + 2] cycloadditions to achieve double S-shaped quadruple helicene-like molecules with high enantioselectivity (up to 96% e.

Damping Control and Experiment on Active Hydro-Pneumatic Suspension of Sprayer Based on Genetic Algorithm Optimization.

High ground clearance self-propelled sprayers usually work in complex road conditions. Due to the large body mass, wide spray boom breath and high center of gravity, the body and spray boom swing sharply during work, which affects operation quality and even endangers safety. This paper proposes a control plan for timely-started active hydro-pneumatic suspension, and designs a fuzzy PID control system based on genetic algorithm optimization.

Organocatalytic Enantioselective Construction of Chiral Azepine Skeleton Bearing Multiple-Stereogenic Elements.

Enantioselective construction of molecules bearing multiple stereogenic elements is increasingly related to the synthesis of enantiopure natural products, pharmaceuticals, and functional materials. However, atom-economical and enantioselective approaches to install multiple stereogenic elements in a small molecular template by limited chemical transformation remain challenging. We describe an organocatalytic enantioselective method for the preparation of polychiral molecules bearing four types of stereogenic elements in fused azepines via vinylidene ortho-quinone methide (VQM)-mediated intramolecular electrophilic aromatic substitution.