Kinetics of the reaction of β‐alkoxyvinyl methyl ketones with amines

Abstract

The kinetics of the reaction of β‐alkoxyvinyl methyl ketones R1O—CR2CH— COCX3 (1a–e)(a, R1CH3, R2H, XH; b, R1C2H5, R2H, XF; c, R1C2H5, R2H, XCl; d, R1R2CH3, XCl;e, R1R2CH3, XF) with aliphatic amines was studied in various solvents. The details of appropriate enaminoketone (2a–d) formation are discussed in terms of an addition–elimination reaction. It is shown that the limiting step of the reaction is the decomposition of a zwitterionic intermediate, and that the observed second‐order reaction rate constants are a function of the solvent's relative permittivity ϵr. At high amine concentrations in non‐polar solvents, the third‐order rate coefficient appears in the reaction rate equation as a consequence of a catalyzed route of the intermediate decomposition. The reaction has low ΔH≠ and high negative ΔS≠ values owing to the formation of a highly polar zwitterionic intermediate. Its lifetimes are determined mainly by the electron‐withdrawing ability of COCX3. Copyright © 2001 John Wiley & Sons, Ltd.

A solvent-free synthesis of beta-enamino trihalomethyl ketones

“…In many of these studies, enaminones are the intermediate formed. Thus, based in previous works, 15 the following sequence of steps appears to afford a satisfactory explanation for the mode of formation of the products (Scheme 2). This reaction involves the initial attack of the amine nitrogen atom on the enone β-carbon with a charge delocalization to the carbonyl group and a subsequent elimination of the alcohol molecule.…”

“…13 One of the most effective methods used to synthesize β-enamino trihalomethyl ketones is the amination reaction of β-alkoxyvinyl trifluoro[chloro]methyl ketones. 14 Vdovenko et al 15 have obtained four trihalomethylated enaminones and one non-halogenated enaminone by a similar route. Recently, we reported the synthesis of trihalomethyl substituted enaminones and trihalomethylated isoxazolines obtained from by the ultrasound promoted reaction of 1,1,1-trihalo-4-alkoxy-3-alken-2-ones with aniline in aqueous media.…”

Efficient preparation of novel N-propargylic β-enaminones from the reaction of β-alkoxyvinyltrihalomethyl[carboxy]ketones and propargylamines

“…Other N-propargylic β-enaminones have been reported in the literature, however only with primary amines. [15][16][17][18] Thus, based on previous works, 23 the following sequence of steps appears to afford a satisfactory explanation for the mechanism of formation of the N,N-arylpropargylic β-enaminones (Scheme 1). This reaction involves the initial attack of the amine nitrogen atom on the enone β-carbon with a charge delocalization to the carbonyl group and a subsequent elimination of the alcohol molecule to furnish the desired products.…”

Efficient synthesis of new 1-[Alkyl(aryl)]-5-(3,3,3-trihalo-2-oxopropylidene)pyrrolidin-2-ones

“…The synthesis of 5-(3,3,3-trifluoro-2-oxopropylidene) pyrrolidin-2-ones from methyl 7,7,7-trihalo-4-methoxy-6-oxo-4-heptenoates and primary amines can be characterised as an Paal-Knorr process for pyrrole heterocyclic from [CCCC + N] building blocks. Mechanistically, it is conceivable that the reaction involves an initial attack from amines to -position, leading to enaminoketone moiety, 14 then an imino intermediate as shown in Scheme 3, which allow the rotation of trihalocarbonyl group around C4-C5 bond on 4-amino-6-oxo-7,7,7-trihalo-4-heptenoates, and intramolecular nucleophilic attack of imino nitrogen to ester carbonyl lead to pyrrolidin-2-ones. …”