摘要：

4-R-Substituted 2-nitro-1-nitrosoethylbenzenes (R = H, [CH.sub.3], O[CH.sub.3], Cl, F) have been synthesized under solvent-free conditions and the mechanism of their tautomerization to 2-isonitroso-1-nitro-2-phenylethanes have been investigated by [sup.1]H NMR spectroscopy. Key words: tautomerization, pseudonitrosite, mechanism, 2-nitro-1-nitrosoethylbenzene, [sup.1]H NMR spectroscopy. Resume : Operant dans des conditions n'impliquant aucun solvant, on a realise la synthese de 2-nitro-1- nitrosoethylbenzenes substitues en position 4 par des groupes R = H, [CH.sub.3], O[CH.sub.3], Cl et F et, faisant appel a la spectroscopie RMN du [sup.1]H, on a etudie leur tautomerisation en 2-isonitroso-1-nitro-2-phenylethanes. Mots-cles : tautomerisation, pseudonitrosite, mecanisme, 2-nitro-1-nitrosoethylbenzene, spectroscopie RMN du [sup.1]H. [Traduit par la Redaction] Shaabani et al. 252 Introduction The discovery of important roles of C-nitroso compounds in various biological metabolic processes has generated a renewed interest in the general chemical properties of nitrosoarenes (1). For example, identification of the nitrosbenzene adduct of hemoglobin as a product of nitrobenzene poisoning (2, 3) and the realization that some amine containing drugs may metabolize to nitroso derivatives (4-7) led to an increased desire to study the biochemical properties of C-nitroso compounds. To this end, many studies have been reported on the fundamental chemistry of C-nitroso compounds under conditions that either stabilize the C-nitroso functionality or enhance their reactivity toward isomerization or reactivity with substrate. There is a considerable variety of synthetic routes available for the preparation of C-nitroso compounds (1, 8-11). However, a major difficulty in C-nitroso chemistry is that the necessary high reactivity of these compounds imposes constraints upon the methods employed for their preparation, particularly with regard to the yield of the desired product. For example, the ease of oxidation of the desired nitroso product to its nitro derivative or its isomerization to corresponding oximes can restrict the choice of solvent for the preparation of these compounds. Solvent-free reactions are of increasing importance because of their potential use in combinatorial chemistry and because they may result in less environmental impact during industrial applications (12, 13). Since tautomerization of C-nitroso compounds to the more stable oximes occurs readily in solutions, we have attempted to find solvent-free reactions that result in selective transformation of the styrene and para-substituted styrenes (1) to 2-nitro-1-nitrosoethylbenzenes (2) without further tautomerization to 2-isonitroso1-nitro-2-phenylethanes (3). (Scheme 1) C-Nitroso compounds are characterized as white solid dimers that result from a N-N connection to give diazene dioxides (14). Since 2-nitro-1-nitrosoethylbenzene derivatives are a monomer and has an asymmetric center, the dimer exists in two diastereomeric isomers namely meso (R,S) and racemate (R,R and S,S) (15). When the dimers are dissolved and (or) heated in an inert low polarity solvent, such as [CH.sub.2][Cl.sub.2] or ether, dissociation into blue (aliphatic) or green (aromatic) monomers usually occurs (1, 16-18). Experimental Melting points were measured on an Electrothermal 9100 apparatus and are uncorrected. Elemental analyses were performed using a Heraeus CHN-O-Rapid analyzer. NMR spectra were recorded on BRUKER DRX-500 AVANCE spectrometer. Temperatures ranged from 298 to 313 K. Infrared spectra were taken on a Shimadzu IR-470 spectrophotometer. Mass spectra were recorded on a FINNIGANMAT 8430 mass...

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