Search results for "Rearrangement"
showing 10 items of 298 documents
Umsetzungen an polyallylalkoholen ein beitrag zur strukturaufklärung der polyacroleine. Polymere acroleine. 23. mitt.
1962
Redoxpolymerisate des Acroleins wurden mit Natriumboranat reduziert und polymere Allylalkohole mit einem Restgehalt von 4 Mol-% Carbonylgruppen erhalten. Sie enthalten auserdem noch etwa 4 Mol-% C—C-Doppelbindungen. Die Polyallylalkohole wurden xanthogeniert und die Zersetzungsgeschwindigkeit im Vergleich zu Propyl- und Polyvinylalkoholxanthogenaten studiert. Neben Aldehydgruppen kommen noch 3–5 Mol-% Ketogruppen in den Redoxpolymerisaten des Acroleins vor. Die Anwesenheit von Doppelbindungen und Ketogruppen in den Polyacroleinen wird durch Nebenreaktionen bei derPolymerisation erklart. Redox-polymers of acrolein were reduced by sodium boranate and polymeric allylic alcohols were obtained w…
Preparation of 4-substituted 1,3-oxathiolan-5-onesviathe sulphenium ion intermediate generated by the pummerer rearrangement
1993
4-Substituted 1,3-oxathiolan-5-ones have been synthesized via the Pummerer rearrangement from the S-oxide of the parent molecule. The 4,5-dione is obtained in the presence of pyridine N-oxide.
Efficient synthesis of novel pyrido[3,2-d]pyrimidine-2,4-diones
2003
Abstract A series of pyrido[3,2- d ]pyrimidine-2,4-diones 5a – g have been synthesized through conversion of 2,3-pyridinedicarboxylic anhydride 1 into half-ester 2 , subsequent Curtius rearrangement and further reaction with amino acids.
Rearrangement of Germacranolides. Synthesis and Absolute Configuration of Elemane and Heliangolane Derivatives from Cnicin
2003
A study of the Cope rearrangement of 15-oxo-germacranolides to 15-oxo-elemanolides has been carried out. The synthesis of two natural elemanolides, isolated from Centaurea paui, and an efficent isomerization of the C-4/C-5 double bond of 15-oxo-germacranolides to form heliangolides are reported. The absolute configuration of all the compounds has been ascertained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Eine oligomeranaloge friessche umlagerung oligomerer 2-acetoxy-1,3-phenylenmethylene
1979
α-Hydro-ω-hydroxypoly(5-chloro-2-hydroxy-1,3-phenylenemethylene)s (1a, b), the oligomeric condensation products from 4-chloro-2,6-bis(hydroxymethyl)phenol and 4-chlorophenol with hydrochloric acid in 1,4-dioxane, could be completely dehalogenated at room temperature and atmospheric pressure with hydrogene/Raney-Ni. The resulting oligomers 2a, b were esterified with acetic anhydride, and the esters 3a, b were subjected to a oligomer analogous Fries rearrangement to form the linear α-hydro-ω-hydroxypoly(5-acetyl-2-hydroxy-1,3-phenylenemethylene)s 4a and 4b. The characterization of the products was mainly done by spectroscopic methods.
Influence of enol acetylation on the photo-fries rearrangement of anortho-acylaryl benzoate
1982
The enol acetate 1b undergoes benzoyl-oxygen bond rupture upon irradiation, giving a mixture of benzophenones 4 and 5. The primary photo-Fries products 2 and 3 could not be isolated, due to a rapid intramolecular transacetylation. The acetophenone 6 rearranges to give the benzophenones 7 and 8 under the same conditions, but the yields are significantly lower than in the former case. Compounds 7 and 8 are separately correlated with 4 and 5 by treatment with acetic anhydride in the presence of pyridine. Einflus der Enol-Acetylierung auf die Photo-Fries-Umlagerung eines Benzoesaure-ortho-acylarylesters Das Enolacetat 1b erleidet bei Bestrahlung Spaltung der Benzoyl-Sauerstoff-Bindung, wobei ei…
Synthesis of (+)-pechueloic acid and (+)-aciphyllene. Revision of the structure of (+)-aciphyllene
2007
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…
ChemInform Abstract: Synthesis of Fluorinated Allylic Amines: Reaction of 2-(Trimethylsilyl)ethyl Sulfones and Sulfoxides with Fluorinated Imines.
2008
A new synthesis of fluorinated allylamines through the reaction of 2-(trimethylsilyl)ethyl sulfones and sulfoxides (as vinyl anion equivalents) with imines and imino esters has been described. The process includes a TBAF-mediated fragmentation of 2-(trimethylsilyl)ethyl sulfones to afford the desired allylic amines. When the reaction is performed with the corresponding sulfoxides, the fragmentation takes place under the addition conditions, affording the final products in a single step.
ChemInform Abstract: A Simple Procedure for the Oxidation of Alcohols Using [Bis(acetoxy)iodo]benzene and a Catalytic Amount of Bromide Ions in Ethyl…
2015
Primary and secondary benzylic alcohols and secondary aliphatic alcohols were oxidized to the corresponding aldehydes and ketones by using [bis(acetoxy)iodo]benzene (BAIB) and a catalytic amount of bromide ions, from tetrabutylammonium bromide or KBr, in ethyl acetate. The catalytic role of the bromide ions was also highlighted in the oxidation of primary aliphatic alcohols and secondary allylic alcohols carried out in the presence of 1 mol% TEMPO.
Diphosphines of dppf-Type Incorporating Electron-Withdrawing Furyl Moieties Substantially Improve the Palladium-Catalysed Amination of Allyl Acetates
2005
Highly active Pd/diphosphine catalytic systems incorporating new, air-stable ferrocenyl-furylphosphines allow nucleophilic allylic amination at room temperature with unprecedented turnover frequencies. For instance, in the presence of 0.01 mol % catalyst the coupling of aniline to allyl acetate occurs at a TOF of more than 10,000 h - 1 ; even the addition of the less nucleophile morpholine to allyl acetate is observed with a TOF of 4250 h - 1 . The amination of the sterically demanding geranyl acetate, a monoterpene derivative of interest in the flavour industry, at low catalyst loadings demonstrates the scope of this methodology, which provides in addition noticeable advantages in terms of…