Nucleophilic Aromatic Substitution Of Hydrogen Research Articles

ChemInform Abstract: Nucleophilic Aromatic Substitution of Hydrogen as a Tool for the Synthesis of Indole and Quinoline Derivatives

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Nucleophilic aromatic substitution of hydrogen: a novel electrochemical approach to the cyanation of nitroarenes.

The nucleophilic aromatic substitution of hydrogen through electrochemical oxidation of the intermediate sigma complexes (Meisenheimer complexes) in simple nitroaromatic compounds is reported for the first time. The studies have been carried out with hydride and cyanide anions as the nucleophiles using cyclic voltammetry (CV) and preparative electrolysis. The cyclic voltammetry experiments allow for the detection and characterization of the sigma complexes and led us to a proposal for the mechanism of the oxidation step. Furthermore, the power of the CV technique in the analysis of the reaction mixture throughout the whole chemical and electrochemical process is described.

Nucleophilic Aromatic Substitution of Hydrogen as a Tool for the Synthesis of Indole and Quinoline Derivatives

Nucleophilic Aromatic Substitution of Hydrogen as a Tool for the Synthesis of Indole and Quinoline Derivatives

Nucleophilic Aromatic Substitution of Hydrogen in the Reaction oftert-Alkylamines with Nitrosobenzenes – Synthesis and NMR Study ofN-(tert-Alkyl)-ortho-nitrosoanilines

The reaction of primary amines bearing tertiary alkyl groups (e.g. R–NH2; R = tBu, 1-adamantyl) with nitrosobenzenes has been found to proceed by oxidative nucleophilic aromatic substitution of hydrogen, thereby affording N-(tert-alkyl)-ortho- and -para-nitrosoanilines. The replacement of hydrogen proceeds more rapidly than the replacement of ortho- or para-nitro or -bromo substituents. With p-nitronitrosobenzene, both ortho-hydrogen atoms are substituted to afford N,N′-di(tert-alkyl)-4-nitro-2-nitroso-1,3-phenylenediamines 8a,b. The addition of oxidizing agents (e.g. MnO2) increases the yield of products. 1H-, 13C-, 14N- and 15N-NMR studies have confirmed the structures of the compounds under investigation. In ortho-nitrosoanilines, the rotamer with the nitroso group syn to the amino group is favored.

Electrophilic and nucleophilic aromatic substitution: Analogous and complementary processes

Analysis of many variants of nucleophilic aromatic substitution of hydrogen proceeding according to an addition—elimination pattern reveals that this is the major reaction pathway, whereas nucleophilic replacement of halogen or another nucleofugal group is the secondary process, i.e.,ipso-substitution. In this respect electrophilic and nucleophilic aromatic substitution can be considered as analogous processes.

A New Route to 4-Aminodiphenylamine via Nucleophilic Aromatic Substitution for Hydrogen: Reaction of Aniline and Azobenzene

A new example of nucleophilic aromatic substitution for hydrogen is described which encompasses reacting aniline and azobenzene (1) in the presence of base under aerobic conditions to generate 4-(phenylazo)diphenylamine (2) in high yield. Monitoring the time course of the reaction under anaerobic conditions revealed that hydrazobenzene (9) was formed as an intermediate in the reaction in equal molar amounts as 2. However, under aerobic conditions 9 was shown not to persist in the reaction mixture. The kinetic effect of isotopic substitution on this reaction was probed by competition experiments utilizing equal molar mixtures azobenzene-d 10 and undeuterated material which gave a k H /k D of 4.6±0.1. It was concluded from these studies that azobenzene was functioning as both the electrophile and oxidant in this reaction. Catalytic hydrogenation of 2 generates 4-amidinodiphenylamine (4-ADPA) (10) and aniline. These reactions form the basis of a novel synthetic route to 4-ADPA which does not utilize halogenated intermediates or reagents and ultimately relies on O 2 as the terminal oxidant in the system

Amination of nitrobenzene via nucleophilic aromatic substitution for hydrogen: direct formation of aromatic amide bonds

The first example of the direct formation of aromatic amide bonds via nucleophilic aromatic substitution for hydrogen is described. Thus, the reaction of benzamide, tetramethylammonium hydroxide dihydrate, and nitrobenzene under anaerobic conditions generates N-(4-nitrophenyl)-benzamide (1) (98%) and azoxybenzene (30%) in isolated yields. In addition, other substituted benzamides and aliphatic amides are shown to function as nucleophiles in this reaction. A mechanism that is consistent with the simultaneous formation of anilide products and azoxybenzene which requires the oxidation of α-complex intermediates by nitrobenzene initially generating nitrobenzene radical anions is proposed. By contrast, when the reaction is run under aerobic conditions, the formation of azoxybenzene is completely inhibited due to the trapping of nitroarene radicals by O 2 . The ability to prepare (1) in high yield and regioselectivity affotds a nouvel route for the direct amination of nitrobenzene that does not require halogenated intermediated or auxiliary leaving groups. Accordingly, treatment of (1) with methanolic ammonia results in the aminolysis of the amide bond producing 4-nitroaniline and regenerates benzamide

The direct coupling of aniline and nitrobenzene: a new example of nucleophilic aromatic substitution for hydrogen

The direct coupling of aniline and nitrobenzene: a new example of nucleophilic aromatic substitution for hydrogen