Aromatic Substitution Of Hydrogen Research Articles

Reaction of N,N-dimethylaniline with N-cyanoazoles according to electrophilic aromatic substitution pattern

N-Cyanoazoles are highly reactive organic compounds and important intermediate products in the synthesis of numerous derivatives containing an azole ring. Owing to high polarity of the cyano group, N-cyanoazoles are capable of acting as electrophilic reagents in electrophilic aromatic substitution reactions. In the present communication we report on the synthesis of some imines via electrophilic aromatic substitution of hydrogen in N,N-dimethylaniline by N-cyanoimidazole, N-cyanobenzimidazole, N-cyano-1,2,3benzotriazole, and N-cyano-2-methylimidazoles. Initial N-cyanoazoles Ia–Id were prepared according to standard procedures. We were the first to demonstrate that the above listed N-cyanoazoles react with N,N-dimethylaniline in the presence of anhydrous aluminum bromide to give para-substituted imines in good yields (65–74%). Azole-containing imines IIa–IId were characterized by sharp melting points and Rf values, and their structure was confirmed by elemental analyses and H NMR spectra. Nitrobenzene was found to be appropriate solvent for carrying out reactions of N-cyanoazoles Ia–Id with N,N-dimethylaniline. High polarity and dissolving power of nitrobenzene ensure homogeneity of the reaction mixture throughout the process. On the other hand, nitrobenzene itself is not involved in the reaction because of the presence of a strong electron-withdrawing nitro group in its molecule. N,N-Dimethyl-4-[azolyl(imino)methyl]anilines IIa–IId (general procedure). Anhydrous aluminum bromide, 4 g, was dissolved in 50 ml of anhydrous nitrobenzene on cooling in an ice–salt bath, and a solution of 15 mmol of N-cyanoazole Ia–Id in 20 ml of anhydrous nitrobenzene was slowly added dropwise under stirring at 6°C. The mixture turned yellow– orange. It was stirred for 1 h, and a solution of 1.9 ml (1.82 g, 15 mmol) of N,N-dimethylaniline in 15 ml of anhydrous nitrobenzene was added. The mixture turned red or blue and was stirred for 4 h, the solvent was distilled off under reduced pressure (3 mm), and the tarry residue was extracted with anhydrous chloroform. The solvent was distilled from the extract on a rotary evaporator under reduced pressure (water-jet pump) at a bath temperature not exceeding 40°C. The crystalline product was stored in a vacuum desiccator over calcium chloride. 4-[1H-Imidazol-1-yl(imino)methyl]-N,N-dimethylaniline (IIa). Yield 2.12 g (66%), mp 186°C (from benzene), Rf 0.56. H NMR spectrum, δ, ppm: 3.2 br.s (6H, NMe2), 5.9 s (1H, NH), 7.2 d (2H, o-H), 7.5 m (2H, 4-H, 5-H), 7.8 m (2H, m-H), 8.1 br.s (1H, 2-H). Found, %: C 67.38; H 6.48; N 26.14. C12H14N4. Calculated, %: C 67.29; H 6.54; N 26.17. 4-[Imino(2-methyl-1H-imidazol-1-yl)methyl]N,N-dimethylaniline (IIb). Yield 2.22 g (65%), mp 168°C (from benzene), Rf 0.65. H NMR spectrum, δ, ppm: 2.5 s (3H, 2-CH3), 3.2 br.s (6H, NMe2), 6.2 s (1H, NH), 7.2 d (2H, o-H), 7.5 m (2H, 4-H, 5-H), 7.6– 7.7 m (2H, m-H). Found, %: C 68.53; H 6.97; N 24.50. C13H16N4. Calculated, %: C 68.42; H 7.02; N 24.56. 4-[1H-Benzimidazol-1-yl(imino)methyl]-N,N-dimethylaniline (IIc). Yield 2.12 g (74%), mp 205°C (from benzene), Rf 0.73. H NMR spectrum, δ, ppm: 3.2 br.s (6H, NMe2), 5.9 s (1H, NH), 7.2 d (2H, o-H), Ht = 1H-imidazol-1-yl (a), 2-methyl-1H-imidazol-1-yl (b), 1H-benzimidazol-1-yl (c), 1H-1,2,3-benzotriazol-1-yl (d). ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 3, pp. 459–460. © Pleiades Publishing, Ltd., 2010. Original Russian Text © A.O. Chunaev, E.A. Stepanov, P.P. Purygin, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 3, pp. 463–464.

Abiotic reaction of iodate with sphagnum peat and other natural organic matter

Previous studies have shown that iodine (including 129I) can be strongly retained in organic-rich surface soils and sediment and that a large fraction of soluble iodine may be associated with dissolved humic material. Iodate (IO3−) reacts with natural organic matter (NOM) producing either hypoiodous acid (HIO) or I2 as an intermediate. This intermediate is subsequently incorporated into the organic matter. Based on reactions of model compounds, we infer that iodine reacts with peat by aromatic substitution of hydrogen on phenolic constituents of the peat. Alternatively, the intermediate, HIO or I2, may be reduced to iodide (I−). The pH (and temperature) dependence of the IO3− reaction (reduction) has been explored with sphagnum peat, alkali lignin, and several model compounds. The incorporation of iodine into NOM has been verified by pyrolysis gas chromatography/mass spectrometry (GC/MS). Model compound studies indicate that reduction of IO3− to HIO may result from reaction with hydroquinone (or semiquinone) moieties of the peat.

Cathodically activated nucleophilic aromatic substitution of hydrogen: a novel electrochemical mechanism.

Cathodically activated nucleophilic aromatic substitution of hydrogen (SNArH) is reported for the first time; the 1,3,5-trinitrobenzene radical anion reacts with the nucleophile N-methylformamide leading to high yields of the sigma H-complex radical anion; this intermediate can be easily oxidised electrochemically by means of a three-electron mechanism giving rise to the nucleophilic aromatic substitution product (NASH product) in good yield.

Electrochemical and XPS investigations of the anodic substitution of an electronic conducting polymer. Cyanation of poly[(1,4-dimethoxybenzene)-co-(3-methylthiophene)

Abstract The oxidation of BF 4 − -doped poly[(1,4-dimethoxybenzene)- co -(3-methylthiophene)] (PDMB-PMeTh) at 1.2 ± 0.1 V (vs. 10 −1 M Ag + |Ag) in dry CH 3 CN+0.2 M NEt 4 CN leads to a new CN-substituted copolymer. Comparative to the PDMB homopolymer, this electrochemical reaction is more efficiently performed, owing to better film properties provided by PMeTh. The electrochemical and XPS data show that the anodic cyanation is achieved specifically on PDMB and results mainly in the aromatic substitution of hydrogen on the DMB unit rather than the replacement of aromatic methoxyl by nitrile. Thus the cyanation mechanism would be different from that demonstrated in solution with DMB, for which p -methoxybenzonitrile was generated. The ratio of the MeTh and DMB units in the copolymer is estimated at 0.4 ± 0.05 and the cyanation results in the linkage of 1.4 ± 0.2 C ≡ N group per DMB unit. Moreover, this study reveals that cations and anions from the electrolyte are strongly retained in the copolymer and partially exchanged after the electrosynthesis, cyanation and chemical treatment steps.