scispace - formally typeset
Search or ask a question
Author

Kamini A. Mishra

Bio: Kamini A. Mishra is an academic researcher from Tallinn University of Technology. The author has contributed to research in topics: Proton NMR & Hydrogen bond. The author has an hindex of 2, co-authored 4 publications receiving 17 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: A new mechanochemical approach for the amide cauldron is reported, which combines solvent-free, atom-efficient, and mechanochemically activated reactions as synthetic strategy for sustainable chemistry.
Abstract: Solvent-free, atom-efficient, and mechanochemically activated reactions have emerged as synthetic strategy for sustainable chemistry. Herein we report a new mechanochemical approach for the amide c...

16 citations

Journal ArticleDOI
05 Apr 2018-Symmetry
TL;DR: This review will present examples from three directions of induction of chirality in or by cucurbituril-type hosts: first, through the incorporation of stereogenic elements into host molecules; second, through complexation with achiral guests, which leads to axial supramolecular chiralities and helical structures; and third,Through the formation of complexes with chiral guests in multi-molecule complexes and induction of supramolescular chorality.
Abstract: Cucurbituril-type hosts are highly symmetric, but there are means to break their symmetry. This review will present examples from three directions of induction of chirality in or by cucurbituril-type hosts: first, through the incorporation of stereogenic elements into host molecules; second, through complexation with achiral guests, which leads to axial supramolecular chirality and helical structures; third, through the formation of complexes with chiral guests in multi-molecule complexes and induction of supramolecular chirality. In addition, a list of chiral guests used in binding studies with cucurbiturils is collected. We would envision that encouraged by the outlined examples of outstanding applications of chiral cucurbituril-supramolecular systems, the boundaries of chiral applications of cucurbiturils would be widened.

12 citations

Journal ArticleDOI
TL;DR: NMR spectroscopy and DFT modeling studies of chiral cyclohexanohemicucurbit[12]uril indicate that the macrocycle adopts a concave octagonal shape with two distinct conformational flexibilities in solution.

4 citations

Journal ArticleDOI
TL;DR: In this article, a set of eighteen organic guests with various functional groups and polarity, namely, thiophenols, phenols, and carboxylic and sulfonic acids, were characterized by Hirshfeld partial charges on acidic hydrogens and their binding by 1H and 19F NMR titrations.
Abstract: Inherently chiral, barrel-shaped, macrocyclic hosts such as cyclohexanohemicucurbit[n]urils (cycHC[n]) bind zinc porphyrins and trifluoroacetic acid externally in halogenated solvents. In the current study, we tested a set of eighteen organic guests with various functional groups and polarity, namely, thiophenols, phenols, and carboxylic and sulfonic acids, to identify a preference toward hydrogen bond-donating molecules for homologous cycHC[6] and cycHC[8]. Guests were characterized by Hirshfeld partial charges on acidic hydrogens and their binding by 1H and 19F NMR titrations. Evaluation of association constants revealed the complexity of the system and indirectly proved an external binding with stoichiometry over 2:1 for both homologs. It was found that overall binding strength is influenced by the stoichiometry of the formed complexes, the partial atomic charge on the hydrogen atom of the hydrogen bond donor, and the bulkiness of the guest. Additionally, a study on the formation of complexes with halogen anions (Cl- and Br-) in methanol and chloroform, analyzed by 1H NMR, did not confirm complexation. The current study widens the scope of potential applications for host molecules by demonstrating the formation of hydrogen-bonded complexes with multisite hydrogen bond acceptors such as cycHC[6] and cycHC[8].

1 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: This review presents an overview of chiral materials in a view of various chiral selectors, including amino acids and their derivatives, proteins, polysaccharides, chiral ligand exchange compounds, Chiral cavity compounds, and chiral ionic liquids, which were applied for the recognition of Chiral molecules.
Abstract: Chirality is a universal phenomenon in nature and an essential attribute of life systems. Chiral recognition has very important research value in many fields. Amino acids and other chiral molecules are the basic components of human body. Understanding the configuration of chiral molecules is beneficial not only to the development of life science, but also to the development of chiral recognition. Compared with other traditional chiral recognition methods, electrochemical methods have the advantages of rapid detection, simple operation, low price, and high sensitivity, which has been widely concerned. In this review, we present an overview of chiral materials in a view of various chiral selectors, including amino acids and their derivatives, proteins, polysaccharides, chiral ligand exchange compounds, chiral cavity compounds (such as cyclodextrin, cucurbituril, calixarene, crown ether), and chiral ionic liquids, which were applied for the recognition of chiral molecules. Besides the chiral recognition mechanisms, some critical challenges and outlooks in the field of electrochemical chiral sensing interfaces are also discussed.

76 citations

Journal ArticleDOI
03 Apr 2019-Symmetry
TL;DR: This minireview provides a promising flexible asymmetric synthesis method for the fabrication of chiral polymer via CPL irradiation, with the hope of obtaining a better understanding of the origin of homochirality on earth.
Abstract: Chirality is a natural attribute nature of living matter and plays an important role in maintaining the metabolism, evolution and functional activities of living organisms. Asymmetric conformation represents the chiral structure of biomacromolecules in living organisms on earth, such as the L-amino acids of proteins and enzymes, and the D-sugars of DNA or RNA, which exist preferentially as one enantiomer. Circularly polarized light (CPL), observed in the formation regions of the Orion constellation, has long been proposed as one of the origins of single chirality. Herein, the CPL triggered asymmetric polymerization, photo-modulation of chirality based on polymers are described. The mechanisms between CPL and polymers (including polydiacetylene, azobenzene polymers, chiral coordination polymers, and polyfluorene) are described in detail. This minireview provides a promising flexible asymmetric synthesis method for the fabrication of chiral polymer via CPL irradiation, with the hope of obtaining a better understanding of the origin of homochirality on earth.

33 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used 1,4-disubstituted 1,2,3-triazoles with [(p-cymene)RuCl₂] for transfer hydrogenation of aliphatic aldehydes and ketones.
Abstract: Coordination of 1,4-disubstituted 1,2,3-triazoles L₁ and L₂ with [(p-cymene)RuCl₂]₂ followed by dehydrochlorination in the presence of a base resulted in the formation of complexes 1 and 2, respectively. Both were tested for the transfer hydrogenation of aldehydes and ketones in air using ecologically benign and cheap ethanol as the hydrogen source in the presence of a catalytic amount of a base. Air-stable complex 1 was proved to be an active catalyst for the transfer hydrogenation of a wide variety of aromatic and aliphatic aldehydes and ketones bearing various functionalities. Catalyst 1 was also effective for the transfer hydrogenation of carbonyls using the simplest primary alcohol, methanol, under aerobic conditions. Under the present catalytic protocol, labile or reducible functionalities such as nitro, cyano, and ester groups were tolerated. Good selectivity was also observed for acyclic α,β-unsaturated carbonyls. However, this catalytic protocol was not selective for 2-cyclohexen-1-one as both alkene and keto moieties were reduced. The transfer hydrogenations are believed to proceed via a ruthenium-hydride intermediate. Finally, transfer hydrogenation of acetophenone using isopropanol as a commonly used hydrogen source was also performed and the sustainable and green credentials of these catalytic protocols utilizing methanol, ethanol, and isopropanol were compared with the help of the CHEM21 green metrics toolkit.

25 citations

Journal ArticleDOI
TL;DR: This direct synthesis platform has been applied to the synthesis of API’s, agrochemicals, and its ability to deliver gram-scale synthesis of active pharmaceuticals and building blocks is demonstrated, all in the absence of a reaction solvent.
Abstract: The direct mechanochemical amidation of esters by ball milling is described. The operationally simple procedure requires an ester, an amine, and substoichiometric KOtBu and was used to prepare a large and diverse library of 78 amide structures with modest to excellent efficiency. Heteroaromatic and heterocyclic components are specifically shown to be amenable to this mechanochemical protocol. This direct synthesis platform has been applied to the synthesis of active pharmaceutical ingredients (APIs) and agrochemicals as well as the gram-scale synthesis of an active pharmaceutical, all in the absence of a reaction solvent.

24 citations

Journal ArticleDOI
08 Apr 2020-Symmetry
TL;DR: Sign-alternating chiral hierarchies created by proteins and nucleic acids are suggested to create the structural basis for the existence of selected mechanical degrees of freedom required for conformational dynamics in enzymes and macromolecular machines.
Abstract: The origin of chiral asymmetry in biology has attracted the attention of the research community throughout the years. In this paper we discuss the role of chirality and chirality sign alternation (L–D–L–D in proteins and D–L–D–L in DNA) in promoting self-organization in biology, starting at the level of single molecules and continuing to the level of supramolecular assemblies. In addition, we also discuss chiral assemblies in solutions of homochiral organic molecules. Sign-alternating chiral hierarchies created by proteins and nucleic acids are suggested to create the structural basis for the existence of selected mechanical degrees of freedom required for conformational dynamics in enzymes and macromolecular machines.

20 citations