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Алкилирование енаминов, β-дикетонов и β-енаминокетонов

Страница 4

Abstract

A method is proposed for introducing one, two, or three alkyl substituents into positions 4 and 6 of the cyclohexane-1,3-dione molecule by successive alkylation under the action of strong bases. (+/-)-Angustione (a natural -diketone) has been synthesized.

A Tandem Amino-Cope Rearrangement/Enamine Alkylation Reaction

Steven M. Allin; Martin A. C. Button; Stephen J. Shuttleworth

Source details: Syn.Lett. 1997, 6 725-727.

Document type: Journal

CODEN: SYNLES

Language: EN

CNR: 6086563

Abstract

Thermally induced (3,3)-sigmatropic rearrangement of 3-amino-1,5-diene substrates occurs to give the corresponding enamine products in high yield and with excellent trans:cis enamine selectivity.The enamine produced during the amino-Cope rearrangement has been directly derivatized, representing the first report of a tandem amino-Cope rearrangement/enamine alkylation reaction.The potential of this novel synthetic strategy is outlined.

N-alkylation of enaminones

John V. Greenhill; Ashraf M. Moten

Source details: Tetrahedron 1983, 39 : 20 3405-3408.

Document type: Journal

CODEN: TETRAB

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.

Название: Алкилирование енаминов, β-дикетонов и β-енаминокетонов
Раздел: Химия
Дата публикации: 2007-01-30 10:57:26
Прочтено: 724 раз

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