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Greener Organic Transformations by Plant-Derived Water Extract Ashes
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
The unique structural appearance, i.e., axial chirality, is the key feature of biaryls for the synthesis of chiral ligands, as, for example, BINOL, (S)-BINAP, (R)-SL-O103-1, (R)-BIPHEMP, and (R)-SLO106-1.90 Therefore, biaryl motifs containing some examples of natural products, drugs, and ligands are highlighted in Figure 10.5. Biaryl skeleton systems have received great attention due to several biological and pharmacological properties like anti-inflammatory, antibiotic, antibacterial, anticancer, antifungal, antimicrobial, antitumor, antagonist, antiproliferative, antihypertension, antituberculosis, and analgesic.81f,85f,91 Some examples of biologically active biaryl derivatives and electron-conducting materials are presented in Figure 10.5.
Gelation-based visual detection of analytes
Published in Soft Materials, 2019
Wangkhem Paikhomba Singh, Rajkumar Sunil Singh
Very recently, Zhang and co-workers have reported chiral discrimination of enantiomeric 1-(2-hydroxynaphthalen-1-yl)naphthalene-2-ol (BINOL) (92). A salicylaldehyde-lysine derived amphiphilic schiff-base gelator (41) gelled solvents like morpholine, aniline, and nitrobenzene. When 1.5 equivalent of (R)-BINOL was added to a morpholine gel of 41, heated, and cooled down to room temperature the gel broke down and a suspension was obtained. Use of (S)-BINOL did not result in gel degradation. Instead, a stable gel was reformed again after a heating-cooling cycle. This observation was concentration dependent. Using less than 1.5 equivalent of BINOL did not disturb the gels’ integrity at all, whereas higher than 3 equivalents of BINOL led to the dissolution of gel irrespective of the enantiomer used.
An experimental and computational study of calamitic and bimesogenic liquid crystals incorporating an optically active [2,2]-paracyclophane
Published in Liquid Crystals, 2018
Richard J. Mandle, John W. Goodby
There are three types of chirality relevant to chemistry and molecular structure; point chirality (e.g. citronellol), axial chirality (e.g. BINOL) and planar chirality, the later arising for a case of chirality that arises from two (or more) disymmetrically substituted non-coplanar rings. Materials containing stereogenic centres (point chirality, e.g. cholesterol benzoate) are ubiquitous in liquid crystals, as are axially chiral materials [1,2]. In a nematic liquid crystal, the addition of a small quantity of a chiral solute leads to the formation of a helical chiral nematic (N*) phase with a helical pitch, P, which is inversely proportional to the solute concentration. Different chiral solutes at the same concentrations can give different pitch lengths, and this is accounted for by defining helical twisting power (HTP) as HTP = (P.c.r)−1, where c is the concentration and r is the optical purity. The introduction of dopants with large HTP values can lead to novel behaviour, such as wide temperature range blue phases [3] and unusual modulated nematic phases in dimeric materials [4]. [2,2]-Paracyclophanes with a single substituent on one aromatic ring exhibit planar chirality, and cannot be converted into their mirror image via rotation as shown in Figure 1. Chiral [2,2]-paracyclophane (such Phanephos) [5] have been employed in enantioselective synthesis, [6] as well as in highly conjugated materials for emission of circularly polarised light [7]. There are few liquid crystals that contain chiral paracyclophanes and the HTP of these materials are rather low (~6–10 μm−1) [8,9]; however, in these examples the bulky paracyclophane protrudes from the mesogenic unit. We envisaged that the steric bulk of the [2,2] paracyclophane group might lead to large values of HTP were it included as a terminal unit rather than as part of the mesogenic core. Both enantiomers of 4-hydroxy[2,2]paracyclophane are conveniently obtained via the enzymatic resolution reported by Cipiani et al. [10], and from this building block we prepared compounds 1 and 2 as shown in Scheme 1.