Реферат: Алкилирование енаминов, бета-дикетонов и енаминокетонов

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.