Refernces
10.1039/b102988f
The research focuses on the synthesis, transition temperatures, and chiral properties of novel achiral and racemic liquid crystals with a bent molecular shape, containing a 1,5-disubstituted 2,3,4-trifluorophenyl unit. These liquid crystals, often referred to as banana-shaped, are of interest due to their potential use in ferroelectric host materials with high dielectric biaxiality. The study extends previous research into liquid crystals with unique physical properties, aiming to understand structure–property relationships and exploit these materials in various applications. The experiments involved detailed synthetic routes to create these complex molecular structures, utilizing reagents such as n-butyllithium, trimethyl borate, and palladium catalysts in铃木耦合反应, among other procedures. The synthesized compounds were then subjected to various analytical techniques, including NMR spectroscopy, infrared spectroscopy, mass spectrometry, and elemental analysis, to confirm their structures and purities. Transition temperatures and phase behaviors were determined using a hot-stage polarizing microscope and differential scanning calorimetry. The research resulted in interesting findings, such as the generation of chirality in achiral materials and the formation of unconventional mesophases in racemic compounds, contributing to the understanding of liquid crystal behavior and their potential applications.
10.3987/COM-09-S(S)100
The study presents a divergent synthesis method for three sulfate derivatives of lamellarin, which are lamellarin 13-sulfate, 20-sulfate, and 13,20-disulfate. These compounds were synthesized using a common intermediate, where the 13-OH and 20-OH of the lamellarin core were differentially protected by MOM and benzyl groups. The synthesis involved a series of chemical reactions, including Suzuki-Miyaura coupling, selective debenzylation, trichloroethylsulfonation, reductive cleavage of the trichloroethyl ester, and others. Key chemicals used in the study include 3,4-dihydroxypyrrole bistriflate, arylboronic acids, MOM-Cl, NBS, tert-BuLi, trimethyl borate, Pd(PPh3)4, Cu2O, quinoline, phenyliodine bis(trifluoroacetate) (PIFA), BF3·OEt2, DDQ, and various solvents and reagents for protection and deprotection steps. These chemicals served to construct the lamellarin core, introduce the sulfate groups selectively, and carry out the necessary transformations to obtain the desired sulfate derivatives. The purpose of these chemicals was to facilitate the synthesis of the lamellarin derivatives, which are of interest due to their unique structures and potential biological activities, particularly as anti-HIV agents.
10.1002/hlca.19870700303
The research focuses on the study of bimolecular nucleophilic substitution at the boron atom in complexes of 2,2’,2”-nitrilotriphenol. The purpose of the study was to investigate the coordination of boron(III) complexes with electronegative ligand atoms and their reactivity towards N-nucleophiles, comparing it to the coordination behavior of carbon and silicon in the same row and diagonally related in the periodic table. The researchers synthesized and studied the reactivity of the boron complex 111, which forms with the ligand 2,2’,2”-nitrilotriphenol, and its subsequent reactions with nitrogen bases like pyridine, quinuclidine, and others. Through temperature-dependent NMR spectroscopy, they found that the reaction is a bimolecular nucleophilic substitution (SN2). The chemicals used in the process included trimethyl borate, 2,2’,2”-nitrilotriphenol, pyridine, quinuclidine, diazabicyclooctane (DABCO), 4-(dimethylamino)pyridine (Me2NPy), and other N-donors, as well as solvents like chloroform (CHCl3), acetonitrile (MeCN), and tetrahydrofuran (THF). The study concluded that the complex 111 is considerably strained and that the reaction entropy is found almost completely on the bimolecular side of the reaction profile, indicating an associative transition state, i.e., an SN2-type mechanism for the nucleophilic substitution.
10.1016/S0040-4039(00)85091-1
The research focuses on the asymmetric Diels-Alder reaction, which is a model for the enantioselective preparation of important tetracycline natural products, specifically targeting chiral anthracyclinone intermediates. The purpose of this study was to develop an efficient, selective, and synthetically flexible method for the synthesis of naturally occurring anthracyclines and related analogue structures. The researchers used a chiral boron reagent derived from B(OMe)3 and (R,R)-(+)-tartaric acid diamide to catalyze the reaction between a naphthoquinone derivative and diene. The process involved the reaction of juglone with trimethyl borate and (R,R)-(+)-diisopropyl tartrate, leading to an intermediate that was then treated with 1-trimethylsiloxy-1,3-diene to afford the chiral adduct with high regio- and stereochemistry.
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