Search results for "arrangement."
showing 10 items of 343 documents
On the Reaction of 3-Bromo-2-nitrobenzo[b]thiophene 13C-Labeled at C-2 with 3-(Trifluoromethyl)aniline: A Preliminary Insight into a Nucleophilic Su…
1997
The results of the title reaction have furnished proofs against a rearrangement of the carbon-atom skeleton and for a nitro group shift in the relevant nucleophilic substitution.
Asymmetric Conjugate Addition of Malonate Esters to α,β-UnsaturatedN-Sulfonyl Imines: An Expeditious Route to Chiral δ-Aminoesters and Piperidones
2013
The asymmetric conjugate addition of malonate esters to α,β-unsaturated N-sulfonyl imines is catalyzed by PyBOX/La(OTf)3 complexes in the presence of 4 Å MS. The reaction gives the corresponding E enamines bearing a stereogenic center at the allylic position with good yields and enantiomeric ratios up to 97:3. This reaction provides a synthetic entry to chiral δ-aminoesters and piperidones.
ChemInform Abstract: Asymmetric Conjugate Addition of Malonate Esters to α,β-Unsaturated N-Sulfonyl Imines: An Expeditious Route to Chiral δ-Aminoest…
2014
The asymmetric conjugate addition of malonate esters to α,β-unsaturated N-sulfonyl imines is catalyzed by PyBOX/La(OTf)3 complexes in the presence of 4 A MS. The reaction gives the corresponding E enamines bearing a stereogenic center at the allylic position with good yields and enantiomeric ratios up to 97:3. This reaction provides a synthetic entry to chiral δ-aminoesters and piperidones.
A contribution to the preparation of phenolic polynuclear compounds with sulfonyl bridges
1964
For the preparation of phenolic di- and tricyclic compounds with sulfonyl bridges the Fries rearrangement is suitable, and for the corresponding products with three and four benzene rings the Friedel-Crafts reaction may be used. The exchange of sulfonyl bridges for methylene bridges produces a marked increase in the melting point.
Disordered hyperuniformity in superconducting vortex lattices
2020
Particles occupying sites of a random lattice present density fluctuations at all length scales. It has been proposed that increasing interparticle interactions reduces long range density fluctuations, deviating from random behaviour. This leads to power laws in the structure factor and the number variance that can be used to characterize deviations from randomness which eventually lead to disordered hyperuniformity. It is not yet fully clear how to link density fluctuations with interactions in a disordered hyperuniform system. Interactions between superconducting vortices are very sensitive to vortex pinning, to the crystal structure of the superconductor and to the value of the magnetic …
Synthesis of Isoxazoline Derivatives through Boulton–Katritzky Rearrangement of 1,2,4-Oxadiazoles
2013
The base-induced rearrangement of 1,2,4-oxadiazoles into isoxazoline derivatives is reported. This represents the first example of a three-atom side-chain rearrangement that involves a saturated CCO side chain at C-3 of the oxadiazole. Nonaromatic 3-amino-isoxazoline derivatives are obtained in good yields. Interestingly, this reaction occurs through the rearrangement of aromatic oxadiazoles to form less stable bonds than those that are broken.
ChemInform Abstract: Synthesis of (+)-Pechueloic Acid and (+)-Aciphyllene. Revision of the Structure of (+)-Aciphyllene.
2008
Abstract 1α H ,7α H ,10α H -Guaia-4,11-dien-3-one and its 1β H ,10β H diastereomer, easily obtained from (+)-dihydrocarvone, are good starting materials for the synthesis of natural guaiane derivatives. Allylic oxidation of the 1α H ,10α H isomer gave as main product its 13-hydroxy derivative and a small amount of (+)-7β-hydroxy-1α H ,10α H -guaia-4,11-dien-3-one, whereas the 1β H ,10β H diastereomer afforded selectively the (−)-7α-hydroxy-1β H ,10β H enantiomer in excellent yield. From the 13-hydroxy derivative (+)-pechueloic acid and (+)-methyl pechueloate were synthesized. Deoxygenation at C 3 of the 1β H ,10β H guaiadienone afforded a guaiadiene with the reported structure for aciphylle…
Volume change characteristics of fine-grained soils due to sequential thermo-mechanical stresses
2019
Know-how of volume change characteristics, VCC, of the fine-grained soils, exposed to thermal stresses, is essential for design of various thermo-active structures. These stresses are known to induce excess pore-water pressure, Δu θ , in the saturated state of such soils, which in turn affects their compression and shear strength characteristics. In this context, through several experimental studies, the effect of thermo-mechanical stress-path, the over-consolidation ratio (OCR) and degree of saturation on VCC (viz., thermally induced volumetric strain, ε vθ , compression and re-compression indices, c c and c r ) of the fine-grained soils has been demonstrated by earlier researchers. Howeve…
Proton Acid-Catalysed Transformations of Estrogen Derivatives: New Results and Some Mechanistic Aspects of theKober Colour Reaction
1994
The 3-O-methylated estrogen derivatives 1a-d and α-estradiol (1e) underwent sulfuric acid-catalysed transformations to furnish the steroids 2–6. The processes involved in the reaction sequence are regioselective sulfonation and, above all, the Wagner-Meerwein rearrangement of the methyl group at C-13. With the objective of obtaining further information on the course of the Kober colour reaction of estrogens, some UV/VIS and ESR spectroscopic investigations were also carried out. Protonenkatalysierte Transformationen von Estrogen-Derivaten: Neue Ergebnisse und einige mechanistische Aspekte der Kober-Farbreaktion Die O-methylierten Estrogenderivate 1a-d und α-Estradiol (1e) reagieren in Schwe…
Some applications of the Chambers isoperimetric inequality
2022
In this paper, using the Chambers isoperimetric inequality, we introduce the notion of weighted rearrangement of a function associated to the measure $f dx$, where $f(x)=e^{g(|x|)}$ for $x \in \mathbb{R}^n}$, with $g$ smooth, convex and even. Then we give some of its applications to variational inequalities and PDEs via weighted symmetrization.