All in a sequence: An organocatalyzed Morita-Baylis-Hillman (MBH)/bromination/[3+2] annulation sequence for highly stereoselective syntheses of bis(spirooxindole)s featuring adjacent spiro-stereocenters is described. The key step is an unprecedented catalytic asymmetric [3+2] annulation of isatin-derived MBH adducts, containing a tetrasubstituted alkene moiety, with isatins.

One‐Pot Tandem Approach to Spirocyclic Oxindoles Featuring Adjacent Spiro‐Stereocenters

Beyond a doubt organocatalysis belongs to the most exciting and innovative chapters of organic chemistry today. Organocatalysis has emerged not only as a complement to metal-catalyzed reactions and to biocatalysis over the last decade, but also provides new asymmetric organocatalyzed reactions that cannot be accomplished by metal- or biocatalyzed reactions so far. A large number of organocatalytic processes are already well established in organic synthesis. Nevertheless, the number of publications in this field is still on the increase; new important results are produced constantly. This review gives a detailed overview of the latest developments and main streams in organocatalyzed asymmetric CC bond formation processes of the last three years. It is intended to outline the most important current findings focused on especially new synthetic methodologies.

Recent Advances in Organocatalytic Methods for Asymmetric C ? C Bond Formation

The method allows the preparation of a broad spectrum of diversely functionalized polycyclic indole skeletons with generally high enantioselectivity.

Highly Enantioselective Friedel-Crafts Alkylation/N-Hemiacetalization Cascade Reaction with Indoles

A rare example of a one-pot process that involves asymmetric triple relay catalysis is reported. The key step is an asymmetric [1,5] electrocyclic reaction of functionalized ketimines. The substrates for this process were obtained in situ in a two-step process that involved the hydrogenation of nitroarenes with a Pd/C catalyst to yield aryl amines and their subsequent coupling with isatin derivatives in a Bronsted acid catalyzed ketimine formation reaction. The electrocyclization was catalyzed by a bifunctional chiral Bronsted base/hydrogen bond donor catalyst. The one-pot process gave the desired products in good yields and with excellent enantioselectivity.

Asymmetric Triple Relay Catalysis: Enantioselective Synthesis of Spirocyclic Indolines through a One‐Pot Process Featuring an Asymmetric 6π Electrocyclization

Enantioselective Friedel–Crafts alkylation for synthesis of 2-substituted indole derivatives

Under different temperatures and concentrations, the diffusion of Vitamin C (VC) in water solution was examined by molecular dynamics simulation. The diffusion coefficients were calculated based on the Einstein equation. The influences of temperature, concentration, and simulation time on the diffusion coefficient were discussed. The results showed that at higher temperature and lower concentration the normal diffusions appear relatively late, but the linear range of mean square displacement curves continues longer than that at lower temperature and higher concentration. At the same temperature, the normal diffusion time increases and the diffusion coefficient decreases as the simulation concentration increases. These simulation results are in good agreement with experiments. Analyses of the pair correlation functions of the simulation systems showed that hydrogen bonds are mainly formed between the hydrogen atoms of VC molecules and oxygen atoms of H2O molecules, rather than between the O atoms of VC molecules and H atoms of H2O molecules. The diffusion coefficient is higher as the interaction between water molecules and VC molecules is stronger when VC concentration is lower. The water in the model systems affects the diffusion of VC molecules by the short-range repulsion of O(H2O)-O(H2O) pairs and the non-bond interaction of H(H2O)-H(H2O) pairs. The short-range repulsion of O(H2O)-O(H2O) pairs is greater when VC concentration is higher, the diffusion of VC is weaker. The greater the non-bond interaction of H(H2O)-H(H2O) pairs is, the higher the VC diffusion is. It is expected that this study can provide a theoretical direction for the experiments on the mass transfer of VC in water solution.

Feng Xue

Papers

Molecular Dynamics Simulation of Diffusion of Vitamin C in Water Solution