Reactions of chloro-substituted enaminoketones,viz., derivatives of imidazolidine nitroxides, with sodium cyanide

Abstract

The reactions of chtoro-substituted enaminoketones, viz., derivatives of imidazolidine nitroxides, with sodium cyanide afford the corresponding nitriles. The reactions proceed through formation of epoxides. The structure of one of these epoxides was confirmed by X-ray diffraction analysis.Key words: nitroxides, enaminoketones, imidazolidines, epo• nucteophilic substitution.Enaminoketones are vinylogs of amides, and their carbonyl groups exhibit reduced reactivity with respect to nucleophilic addition, j Derivatives of imidazolidine nitroxides 1 are no exception.Thus. compounds 1 were prepared by the reactions of imidazolidine 2 with esters in the presence of lithium diisopropylamide (LDA)_ z-4 In no case was the formation of compounds 3, which are products of the addition of two molecules 2 to the ester molecule, observed whatever the order in which the reagents were mixed and their ratio. Enaminoketones 1 do not react with amines and sodium borohydride. In tile reactions of compounds I with hydroxyiamine, only the nitroxyl group was reduced to the hydroxylamino group, while the carbonyl group remained intact. 5 Only under rather severe conditions, viz., upon refluxing of enaminoketones 1 with hydroxylamine hydrochloride in pyridine, did the keto group also enter into the reaction: however, the heterocycle was initially cleaved and the subsequent reaction of the hydroxylamino group with the carbonyl group occurred as an imramolecular process to form pyrroline derivative 4 (Scheme 1). 3 Therefore, the addition of a nucleophile at the carbonyl group is less probable than the nucleophilic attack on the carbon atom bound to the nitrogen atom.Previously, we have demonstrated that in the reactions of enaminoketones 1 with hypohalogenites in an aqueous-methanolic solution at 0 ~ the enaminoketone group was readily cleaved to form halomethyl derivatives of 3-imidazolidine. 6 Apparently, the scheme of this reaction involves the initial formation of mono-or dihalogen derivatives followed by the nucleophilic attack on the carbon atom of the carbonyl group. The possibility of this reaction proceeding according to the abovementioned scheme was confirmed by the conversion of bromo-substituted enaminoketone 5 (X = Br) into bromomethyl derivative 6 (X = Br) in the reaction with sodium methoxide (Scheme 2). The somewhat surprising thing is that compound 6 (X = Br) did not further react with an excess of sodium methoxide. Note that unsubstituted enaminoketone la (R = Ph) did not react with sodium methoxide under these conditions and even

A New Class of Enehydroxylamino Ketones − (R)‐2‐(1‐Hydroxy‐4,4,5,5‐tetraalkylimidazolidin‐2‐ylidene)ethanones: Synthesis and Reactions

“…ref. [30] ) isomers (or conformers) and that the geometry of the exocyclic double bond cannot easily be determined from NMR spectroscopic data. The equilibrium may be slow or fast on the NMR timescale, so determination of the true geometry of 1 or of the isomer ratio and quantity is not an easy task.…”

“…We had previously found that both enaminones and enehydroxylamino ketones react with N-chloro-and Nbromosuccinimides to form mono-or dihalo derivatives depending on the substrate/reagent ratio. [7,30,41] Treatment of 1 with an equimolar amount of N-chlorosuccinimide (NCS) gives moderate yields of monochloro derivatives 20, of low stability and not isolable in pure form (cf. ref.…”

Copper(II) Cubane Complexes Built from Electro‐ and Photosensitive β‐Aminovinyl Trifluoromethyl Ketone Ligands

“…Our research is currently devoted to the elaboration of ligands able to bring additional properties to the magnetic core with the expectation that both properties could interact cooperatively. [8,[16][17][18][19][20][21][22][23][24][25][26] Their potential for diverse coordination chemistry [27][28][29][30][31][32][33][34][35][36] combined with appropriate pendant organic functionalities (a photosensitive unit, a stable radical, an electron donor, a luminescent unit or a biomolecule) make them attractive for the design of new generations of original materials. [8] On the other hand, their ability to coordinate a large panel of transition-metal ions have led to the preparation of a number of metallomesogens with interesting liquid-crystal properties [9][10][11][12] or highly-active catalysts for olefin polymerization, including fluorinated enaminones.…”

Nucleophilic Substitution of Chloro‐Substituted Enaminones that are Derivatives of Imidazolidine Nitroxides − The Catalytic Effect of the Cyanide Ion

“…[2] Reaction of enaminones 1 with azide ion proceeds in a similar manner, but the resulting azides 3 are unstable and are transformed spontaneously into monoimines of α-diketones (4). [3] A study of these reactions resulted in the conclusion that halo-substituted enaminones 1 react with these nucleophiles to form the intermediate epoxides.…”

“…The synthesis of the starting enaminones 1 was performed as published in ref. [2] and that of the dichloro derivative 6 as in ref. [8] 2-Chloro-2-(1-methoxy-2,2,5,5-tetramethylimidazolidin-4-ylidene)-1-phenylethanone (5): Enaminone 1a (0.5 g, 1.7 mmol) was added portionwise to a solution of methylmagnesium iodide, prepared from Mg (0.2 g, 8.3 mmol) and CH 3 I (0.53 mL, 8.5 mmol) in anhydrous diethyl ether (20 mL).…”