Search

Recently supramolecular chirality has received increasing interest due to its potential applications in enantioselective sensors and chromatographic separation of enantiomers. The appearance of such chirality results from the helical organization of molecules manifested by H-bonding interactions, weak van der Waals forces, and electrostatic forces. In recent years a lot of interest has been focused towards the synthesis of chiral conjugated polymers such as polyacetylene, polythiophene, polypyrrole, polyaniline (PANI), and poly(p-phenylene vinylene) due to their potential applications in circularly polarized electroluminescence and chiral electrode for asymmetric synthesis. Among these chiral PANI is desirable because it is inexpensive, environmentally stable, and can be readily doped and dedoped using simple acid–base stimuli. Besides PANI does not require any synthetic steps before the polymerization of achiral aniline and totally relies on the preferential formation of either right- or left-handed helix of the polymer backbone due to the presence of a chiral dopant in the reaction medium. Different types of chiral acids have been used for the creation of helical polyaniline using different methods. This review paper presents a detailed discussion of different methods of synthesizing helical/chiral polyaniline, different types of dopants used for chirality induction, chirality measurement by circular dichroism spectroscopy, parameters controlling induction and stabilization of chirality in PANI, and application of chiral polyanilines in diverse areas such as enantiomer separation, enantioselective synthesis, chiral nanocomposites, and microwave absorption. [ABSTRACT FROM AUTHOR]

Comprehensive Summary The 21st century has witnessed a continuous evolution in the development of boron‐stereogenic chemistry. Since the 1990s, various innovations for the synthesis of tetracoordinate boron‐stereogenic compounds, which exhibited great potential applications, have been demonstrated by synthetic chemists. This paper reviews the significant progress and recent advances towards the assembly of enantioenriched boron‐stereogenic compounds, and hopes to shed light on new perspectives and inspire further research in this emerging field. [ABSTRACT FROM AUTHOR]

Highly symmetrical and aesthetically pleasing molecules have attracted the attention of organic chemists. We synthesized new highly symmetric stereogenic π-conjugated macrocycles with planar or axial chirality. Macrocyclic oligomers synthesized by Yamamoto coupling or Suzuki–Miyaura cross-coupling from the π-unit containing chirality. These cyclization reactions gave multiple oligomers in relatively high yields. We then elucidated their structures and investigated their chiroptical properties, including circular dichroism (CD) and circularly polarized luminescence (CPL). Because of the selection rule for rigid and symmetric structures, these macrocycles exhibit a high dissymmetry factor (gabs or glum) for circularly polarized light in CD or CPL. Several rigid cyclic compounds retain a highly symmetric structure in the excited state and exhibit higher glum values than common chiral organic compounds. This Account provides a brief background regarding chiroptical properties, followed by a summary of the various macrocycles synthesized in this study. We are glad if this Account will be a source of ideas not only for chemists working with π-conjugated compounds, but also for synthetic chemists working with chiral compounds, especially those engaged in asymmetric synthesis. 1 Introduction 2 Brief Description of Chiroptical Properties 3 Stereogenic Macrocycle Based on [2.2]Paracyclophane 3.1 Stereogenic Double-decker Oligothiophene 3.2 Stereogenic Biselenophene Macrocycle 3.3 Helical Oligophenylene Linked with [2.2]Paracyclophane 4 Stereogenic Macrocycle Based on Binaphthyl 4.1 Cyclic Oligomer of Chiral Binaphthyl 4.2 Doubly Twisted Binaphthyl Dimer 4.3 Cyclic Oligomer of Binaphthyl Extended with Paraphenylene 4.4 Curved Helical Paraphenylene Anchoring Chiral Binaphthyl 4.5 Binaphthyl-Hinged [5]-Helicene 5 Summary [ABSTRACT FROM AUTHOR]

Chirality constitutes an inherent attribute of nature. The catalytic asymmetric synthesis of molecules with central, axial, and helical chirality is a topic of intense interest and is becoming a mature field of research. However, due to the difficulty in synthesis and the lack of a prototype, less attention has been given to planar chirality arising from the destruction of symmetry on a single planar ring. Herein, we report the catalytic asymmetric synthesis of planar-chiral dianthranilides, a unique class of tub-shaped eight-membered cyclic dilactams. This protocol is enabled by cinchona alkaloid-catalyzed (dynamic) kinetic resolution. Under mild conditions, various C2- or C1-symmetric planar-chiral dianthranilides have been readily prepared in high yields with excellent enantioselectivity. These dianthranilides can serve as an addition to the family of planar-chiral molecules. Its synthetic value has been demonstrated by kinetic resolution of racemic amines via acyl transfer, enantiodivergent synthesis of the natural product eupolyphagin, and preliminary antitumor activity studies. Chirality has long fascinated chemists, but asymmetric synthesis has largely focused on central, axial, and helical chirality to date. Here, the authors synthesize dianthranilides with planar chirality, via cinchona alkaloid-catalyzed (dynamic) kinetic resolution. [ABSTRACT FROM AUTHOR]

In this study, the design and asymmetric synthesis of a series of chiral targets of orientational chirality were conducted by taking advantage of N-sulfinylimine-assisted nucleophilic addition and modified Sonogashira catalytic coupling systems. Orientational isomers were controlled completely using alkynyl/alkynyl levers [C(sp)-C(sp) axis] with absolute configuration assignment determined by X-ray structural analysis. The key structural element of the resulting orientational chirality is uniquely characterized by remote through-space blocking. Forty examples of multi-step synthesis were performed, with modest to good yields and excellent orientational selectivity. Several chiral orientational amino targets are attached with scaffolds of natural and medicinal products, showing potential pharmaceutical and medical applications in the future. [ABSTRACT FROM AUTHOR]