165094 (739222), страница 3
Текст из файла (страница 3)
Language: EN
CNR: 5609239
Abstract
The base catalyzed N-alkylation of a series of primary and secondary enaminones has been examined in detail.The enaminone anion was found to be a weak nucleophile.Best results were obtained in tetrahydrofuran or dioxane with sodium hydride and an alkyl iodide.
Alkylation of Ketones and Aldehydes via their Nitrogen Derivatives
James K. Whitesell; Marilyn A. Whitesell
Source details: Synthesis 1983, 7 517-536.
Document type: Journal
CODEN: SYNTBF
Language: EN
CNR: 5572282
Abstract
In this review, methods for the alkylation of the aldehydes and ketones via formation of nitrogen derivatives such as enamines, metallated imines (imine anions), metallated N,N-dialkylhydrazones (N,N-dialkylhydrazone anions), dimetallated oximes (oxime dianions), and metallated O-methyloximes (O-methyloxime anions) are described.Scope, limitations, and advantages or disadvantages of the methods over comparative reactions of enolates are also mentioned.
Intramolecular Photoarylations of N-(Haloaryl)ethyl β-Enaminones
Tammy Tiner-Harding; Patrick S. Mariano
Source details: J.Org.Chem. 1982, 47 : 3 482-485.
Document type: Journal
CODEN: JOCEAH
Language: EN
CNR: 5570323
Abstract
The photochemistry of several N-(haloaryl)ethyl β-enaminones was investigated in order to develop methods for preparation of tricyclic enaminone systems.The efficiencies of intramolecular photoarylations of the haloaryl systems were found to be dependent upon the wavelength of irradiation.Accordingly, irradiations of the haloaryl β-enaminones 9a,c,d,f with Pyrex-filtered light leads to formation of the reduced N-cyclized and C-cyclized products 9b or 9e, 8a or 8b, and 10a or 10b, respectively. The major products in these processes are the reduced materials.In contrast, irradiations of the bromoaryl enaminones 9c or 9f with Vycor-filtered light results in high yielding conversions to the C-cyclized tricyclic enaminones 10a and 10b in synthetically useful yields ranging from 50% to 85%.A discussion of reasons for these wavelength dependencies is given in terms of excited-state discrimination in these bichromophoric systems.Possible reaction mechanisms are considered.The origin of another major product, 11, generated by irradiation of 9f with Vycor-filtered light, is also discussed.
Regioselective control of N-aryl enaminone alkylation
Denise Dugat; Daniel Gardette; Jean-Claude Gramain; Bertrand Perrin
Source details: Bull.Soc.Chim.Fr. 1994, 131 : 1 66-70.
Document type: Journal
CODEN: BSCFAS
Language: EN
CNR: 5851695
Abstract
The regioselectivity of the C-alkylation of unsubstituted N-aryl enaminones prepared from cyclohexane-1,3-dione may be controlled by the nature of the base used.Our results indicate that monoalkylation is completely regioselective; lithium diisopropylamide leads to α’-alkylated compounds while lithium bis(trimethylsilyl)amide affords γ-alkylated products.In contrast, alkylation of α’- or γ-substituted compounds always occurs in the α’-position regardless of the base.
Regiospecificity and Regioselectivity of the Alkylation, Acylation, Sulfenylation and Sulfonylation of Pyrrolidine Enaminones
Thomas Burgemeister; Gerd Dannhardt; Ernst Eibler; Brigitte Paulus; Klaus Ziereis
Source details: Arch.Pharm.(Weinheim Ger.) 1988, 321 : 345-348.
Document type: Journal
CODEN: ARPMAS
Language: GE
CNR: 5807249
Abstract
Different methods to modify a pyrrolidine enaminone regiospecifically or regioselectively at the N- and C-atom, respectively, are described.All compounds have been isolated and characterized, in case of the alkylation reactions the ratio of regioisomers is determined by HPLC.NOE experiments are performed in order to prove the configuration of some adducts.
Reactivity of N-substituted enaminones with unsaturated carbonyl compounds
Esther Caballero; Blanca Madrigal; Manuel Medarde; Pilar Puebla; Zoila Honores; et al.
Source details: Ach.Mod.Chem. 1998, 135 : 4 457-474.
Document type: Journal
CODEN: ACMCEI
Language: EN
CNR: 6101721
Abstract
The reactivity of enaminones of 2-aminoethanol and 2-aminoethanothiol towards polyelectrophilic reagents has been studied.A brief overview of our previous results with this enaminones, which allowed us to describe new synthesis of fused heterocycles, is included. In the present work, only the formation of C-C bond is a common feature of the reaction, to produce derivatives or simple heterocycles.Although no fused heterocycles were obtained, the reaction products have complex functionalization which will allow further cyclization to such a class of polyfused systems.
Reactions between Enaminones and Enones. Part 2. C versus N-Alkylation with Cyclohex-2-enone. Structure Confirmation by Reduction of a Dienaminone Derivative of Dehydrated Dimedone Dimer
Ibrahim Chaaban; John V. Greenhill; Mohamed Ramli
Source details: J.Chem.Soc.Perkin Trans.1 1981, 3120-3124.
Document type: Journal
CODEN: JCPRB4
Language: EN
CNR: 5625982
Abstract
Primary and secondary enaminones derived from cyclohexane-1,3-dione, dimedone, and acetylacetone react with cyclohexenone to give exclusively C-alkylated derivatives.In every case the products form carbinolamines which exist as 1-hydroxy-2-azacyclo[3.3.1]nonenes.This was confirmed in some examples by formation of an extra ring between nitrogen and oxygen.A series of dienaminones were prepared from 2-(5,5-dimethyl-3-oxocyclohex-1-enyl)-5,5-dimethylcyclohexane-1,3-dione and one of these was reduced to give an azanonene identical with that from C-alkylation.
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