Search results for "Organo"

Nitroenynes as Electrophiles in Organocatalysis and their Application in the Synthesis of Chiral Heterocycles

2021

Nitroenynes are an interesting electrophile in asymmetric organocatalysis, due to the versatility of the functional groups present in its structure. This review covers the organocatalytic examples using this electrophile and its application for the synthesis of chiral heterocycles.

Recent Advances in Catalytic Enantioselective Synthesis of Pyrazolones with a Tetrasubstituted Stereogenic Center at the 4-Position

2020

AbstractPyrazolone [2,4-dihydro-3H-pyrazol-4-one] represents one of the most important five-membered nitrogen heterocycles which is present in numerous pharmaceutical drugs and molecules with biological activity. Recently, many catalytic methodologies for the asymmetric synthesis of chiral pyrazolones have been established with great success, specially, for the synthesis of pyrazolones bearing a tetrasubstituted stereocenter at C-4. This review summarizes these excellent research studies since 2018, including representative examples and some mechanistic pathways explaining the observed stereochemistry.1 Introduction2 Catalytic Enantioselective Synthesis of Chiral Pyrazolones with a Full Car…

Asymmetric Organocatalytic Synthesis of aza-Spirocyclic Compounds from Isothiocyanates and Isocyanides

2021

The spirocyclic motif is present in natural products, chiral ligands, and compounds of pharmacological interest. Isothiocyanates as well as isocyanides bearing electron-withdrawing groups in the α-position can be deprotonated and react as formal dipoles on account of the presence of a nucleophilic carbanion and an electrophilic atom in the isothiocyanate or isocyanide functional groups. In the last years a number of procedures involving the formal [3+2] cycloaddition reaction of isothiocyanates or isocyanides with cyclic compounds bearing electrophilic exocyclic double bonds have been developed for the enantioselective synthesis of aza-spirocyclic compounds. Among them, organocatalysis has …

Equilibrium structure of LiCCH

2000

Controlling magnetism with light in zero orbital angular momentum antiferromagnet

2023

Antiferromagnetic materials feature intrinsic ultrafast spin dynamics, making them ideal candidates for future magnonic devices operating at THz frequencies. A major focus of current research is the investigation of optical methods for the efficient generation of coherent magnons in antiferromagnetic insulators. In magnetic lattices endowed with orbital angular momentum, spin-orbit coupling enables spin dynamics through the resonant excitation of low-energy electric dipoles such as phonons and orbital resonances which interact with spins. However, in magnetic systems with zero orbital angular momentum, microscopic pathways for the resonant and low-energy optical excitation of coherent spin …

Refrigerated Fruit Juices: Quality and Safety Issues

2007

Fruit juices are an important source of bioactive compounds, but techniques used for their processing and subsequent storage may cause alterations in their contents so they do not provide the benefits expected by the consumer. In recent years consumers have increasingly sought so-called "fresh" products (like fresh products), stored in refrigeration. This has led the food industry to develop alternative processing technologies to produce foods with a minimum of nutritional, physicochemical, or organoleptic changes induced by the technologies themselves. Attention has also focused on evaluating the microbiological or toxicological risks that may be involved in applying these processes, and t…

Structure and Sensory Analyses of Tainting Substances in Finnish Freshwater Environments

1988

GC/MS/SNIFF/TASTE methods have been used in Finland to identify the causes of three tainting problems in water and one in fish nets. Structure determination was often verified by comparison with authentic compounds. Algal growth was implicated to be the source of geosmin and MIB in river water in Northern Finland and was associated with the appearance of tainting problems in raw water and reservoir water in Åland county. Terpenoids (e.g. camphor), degradation products of natural lipids (e.g. aldehydes, ketones and unsaturated aliphatic compounds) and volatile organohalogen compounds were frequently found in contaminated water but showed minor tainting effects compared to geosmin and MIB. Di…

Complexes of organometallic compounds. L. The correlation between 119Sn mössbauer isomer shifts and calculated partial charges on tin in adducts of t…

1981

Abstract The relationship between Mossbauer isomer shifts, δ, and atomic charges on tin, QSn has been studied for homologous series RnSnhal4−n· L2 [ n = 0−3; L2 = donor atoms of 1, 2-bis(dipheylphosphino)ethane, N, N′-ethylenebes(salicylideneimine) and N, N′-ethylenbes(acetylacetoneimine)] and Snhal4· 2PR3. Semiempirical values of QSn have been calculated by two methods based on the concept of orbital electronegativity equalization upon bond formation. Linear correlations δ/QSn are obtained, which can be function of the coordination number of the metal atom, for terms of the series characterized by different orbital electronegativities of atoms directly bound to tin. Deviations occur for ad…

C−C Cross-Couplings from a Cyclometalated Au(III) C∧ N Complex: Mechanistic Insights and Synthetic Developments

2021

Abstract In recent years, the reactivity of gold complexes was shown to extend well beyond π‐activation and to hold promises to achieve selective cross‐couplings in several C−C and C−E (E=heteroatom) bond forming reactions. Here, with the aim of exploiting new organometallic species for cross‐coupling reactions, we report on the Au(III)‐mediated C(sp2)−C(sp) occurring upon reaction of the cyclometalated complex [Au(CCH2N)Cl2] (1, CCH2N=2‐benzylpyridine) with AgPhCC. The reaction progress has been monitored by NMR spectroscopy, demonstrating the involvement of a number of key intermediates, whose structures have been unambiguously ascertained through 1D and 2D NMR analyses (1H, 13C, 1H‐1H CO…

Organoplatinum(II) Complexes Self-Assemble and Recognize AT-Rich Duplex DNA Sequences

2021

The specific recognition of AT-rich DNA sequences opens up the door to promising diagnostic and/or therapeutic strategies against gene-related diseases. Here, we demonstrate that amphiphilic PtII complexes of the type [Pt(dmba)(N∧N)]NO3 (dmba = N,N-dimethylbenzylamine-κN, κC; N∧N = dpq (3), dppz (4), and dppn (5)) recognize AT-rich oligonucleotides over other types of DNA, RNA, and model proteins. The crystal structure of 4 shows the presence of significant π-stacking interactions and a distorted coordination sphere of the d8 PtII atom. Complex 5, containing the largest π-conjugated ligand, forms supramolecular assemblies at high concentrations under aqueous environment. However, its aggreg…