Organic & Biomolecular Chemistry Blog

Over the past few decades a lot of interest has been given to macrocycles with a twisted structure that has a preferred direction and show an optical chirality due to their possible uses in many areas such as in materials for chiral recognition.

In this HOT paper Eiji Yashima and colleagues from Nagoya University report the design and synthesis of three helically twisted [1 + 1]macrocycles, whose chirality can be controlled by acid–base interactions and zinc coordination.

Yashima et al. connect the twisted [1 + 1]macrocycles using via o-, m-, and p-linkages and use chiral amidinium–carboxylate salt bridges as a versatile structural motif to control the twisting motion of the macrocycles.

Find out all of the details of this study by downloading this paper. It’s free to access for 4 weeks.

Synthesis of helically twisted [1 + 1]macrocycles assisted by amidinium–carboxylate salt bridges and control of their chiroptical properties
Yuji Nakatani, Yoshio Furusho and Eiji Yashima
DOI: 10.1039/C2OB27054D

In this HOT communication, Yanli Zhao and co-workers from Nanyang Technological University report the construction of a series of dynamic supramolecular self-assemblies based on covalently linked pillar[5]arene trimers. These trimers have three binding sites, each capable of interacting with a bivilogen bipyridinium functionality. In solution these molecules assemble into complex structures.

Zhao et al. use techniques including dynamic light scattering, scanning electron microscopy and transmission electron microscopy to permit the detailed examination of these elegant supramolecular assemblies.

Acetone mixtures of the two components produce small building blocks at concentrations of 0.5 mM, with expanding aggregates rolling into hollow nanospheres when concentrations approach 1 mM. Beyond this concentration large flat layers are created, which stack at concentrations in excess of 2 mM. In essence the system demonstrates a reversible multidimensional transformation from 0D to 3D, and is an example of controlled dynamic self-assembly.  This represents a novel method for developing new functional materials with a switchable morphology control.

Published on behalf of Steve Moore, Organic & Biomolecular Chemistry web science writer.

Researchers in China have developed a simple and effective way to construct spiropyrazolones, stereochemically complex and challenging structural motifs found in many biologically active molecules.

Spirocyclic structures are bicyclic systems where the two rings are connected through a single atom, usually a quaternary carbon. Due to their complex three-dimensional architecture, they are important molecular subunits in organic chemistry. They can be very difficult to assemble, especially in an asymmetric and atom-economic fashion.

3-Pyrazolones are privileged structures and molecules that contain them have been found to possess a huge range of useful biological effects such as antibiotic and anti-tumour properties. In addition to their marked medicinal potential, they have also found use as dyes and anti-corrosives.

For these reasons, methods for the construction of pyrazolone derivatives have attracted intense interest from organic chemists in recent years. The synthesis of optically active pyrazolones, including spiropyrazolones, is particularly challenging with only a handful of syntheses reported in the current literature.

Professor Rui Wang, of the State Key Laboratory of Applied Organic Chemistry, Lanzhou University in China and his research group have been looking into new ways to make spirocyclic compounds, using organocatalytic cascade reactions.

In their latest HOT PAPER, they turn their attention to the construction of spiropyrazolones. A very elegant organocatalytic double Michael cascade reaction between unsaturated ketones and unsaturated pyrazolones yields the desired spiropyrazolone core structure in excellent diastereo- and enantioselectivities.

This reaction provides rapid entry into stereochemically complex spiropyrazolone derivatives and will no doubt prove useful in the manufacture of future medicines and materials.

Published on behalf of Annabella Newton, Organic & Biomolecular Chemistry web science writer.