Oxidation of aromatic amines with chromyl chloride-I

Synthesis of tris­, tetrakis­, and pentakisazo dyes and their application to guest–host liquid crystal displays

“…4-[4-(4-Butylphenylazo)-3,5-dimethylphenylazo]-3,5-dimethylaniline 3b. Yield 56%; mp 189±190 ³C; d H 0.93 (3H, t, J 7.5), 1.35 (2H, sextet, J 7.5), 1.62 (2H, quintet, J 7.5), 2.39 (6H, s), 2.43 (6H, s), 2.70 (2H, t, J 7.5), 3.46 (2H, br s), 6.63 (2H, s), 7.44 (2H, d, J 8.4), 7.57 (2H, s), 7.82 (2H, d, J 8.4); m/z 413 (M z ; 89%), 252 (13), 148 (18), 120 (100), 91 (24).…”

“…4 The chemical structures of all the dichroic azo dyes are limited to the derivatives with strong electron donor groups (N,Ndialkylamino-or hydroxy-), as these are necessary to facilitate the azo coupling reaction. Many kinds of oxidizing reagents such as lead(IV) acetate, 7 bleaching powder, 7a silver(II) oxide, 8 silver(II) carbonate, 9 sodium hypochlorite, 10 manganese(IV) oxide, 11 Nchloroacetoanilide, 12 chromyl chloride, 13 2,2'-bipyridylchromium(VI) peroxide, 14 iodobenzene diacetate, 15 copper salts, 16 barium salts, 17 potassium hexacyanoferrate(III), 18 and an oxygen molecule 19 have been reported to form azobenzenes. 5 However, no detailed information concerning the properties of the polyazo dyes has been presented.…”

“…These products are not obtained by the diazotisation-coupling reactions. Many kinds of oxidizing reagents such as lead(IV) acetate, 7 bleaching powder, 7a silver(II) oxide, 8 silver(II) carbonate, 9 sodium hypochlorite, 10 manganese(IV) oxide, 11 Nchloroacetoanilide, 12 chromyl chloride, 13 2,2'-bipyridylchromium(VI) peroxide, 14 iodobenzene diacetate, 15 copper salts, 16 barium salts, 17 potassium hexacyanoferrate(III), 18 and an oxygen molecule 19 have been reported to form azobenzenes. It has also been reported that the combination of the substrates and oxidizing reagents drastically changes the yields of the products.…”

Exploring New Parameter Spaces for the Oxidative Homocoupling of Aniline Derivatives: Sustainable Synthesis of Azobenzenes in a Flow System

“…46,48,50 The syntheses of multisubstituted azobenzene derivatives are quite scarce in the literature, possibly because of the tremendous steric hindrance generated by the functional groups. 38,39,50,97 However, it emerged that di-and trisubstituted aniline derivatives also displayed excellent reactivities in the corresponding homocopuling reactions. Even diortho-substituted anilines were converted quantitatively to the desired adducts (entries 12 and 13), and all the corresponding multisubstituted derivatives were achieved in excellent yields of 89−93% (entries 11 −14).…”

Activated Carbon-Promoted Dehydrogenation of Hydroquinones to Benzoquinones, Naphthoquinones, and Anthraquinones under Molecular Oxygen Atmosphere

“…Yield 65% (39 mg, 0.33 mmol), brown solid, mp 50.2–50.7 °C (lit . mp 56.5 °C); IR (neat) 527, 532, 540, 547, 553, 559, 565, 778, 830, 915, 972, 1096, 1109, 1197, 1280, 1315, 1372, 1577, 1642, 1658, 3044, 3054; 1 H NMR (400 MHz, CDCl 3 ) δ = 7.32 (d, J = 2.4 Hz, 1H), 6.97 (d, J = 10.1 Hz, 1H), 6.83 (dd, J = 10.1, 2.4 Hz, 1H); 13 C­{ 1 H} NMR (100 MHz, CDCl 3 ) δ = 184.5, 179.1, 138.1, 137.5, 136.6, 135.8.…”