The synthesis of azo compounds from nitro compounds using lead and triethylammonium formate

Azobenzenes—synthesis and carbohydrate applications

“…[92][93][94][95][96][97][98][99] Between the two methods described above, two classes of derivatives can be obtained: the symmetrical and the dissymmetrical azobenzenes. The synthesis of symmetrical azobenzene derivatives was effected by: (i) oxidation reactions of aromatic primary amines; [19][20][21][22][23][24][25][26][27][28][29][30] (ii) reduction reactions of aromatic compound having nitro groups; [32][33][34][35][36] (iii) diazo-coupling via diazonium salts; [54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71] and (iv) coupling reactions with arenediazonium salts. 100,101 The synthesis of dissymmetrical azobenzene derivatives was effected by: (i) oxidation reactions of aromatic primary amines; 31 (ii) coupling of primary arylamines with nitroso compounds (Mills reaction); [37]…”

“…Nitrobenzene (46) and lead powder in methanol in the presence of triethylammonium formate furnished the azobenzene (1) in 92% yield (Scheme 18). 34 Gowda et al proposed 34 that the initial reduction of the nitro compound furnished a hydroxylamine as a reaction intermediate.…”

Water as a Direct Hydrogen Donor in Supercritical Carbon Dioxide: A Novel and Efficient Zn‐H2O‐CO2 System for Chemo‐selective Reduction of Nitrobenzenes to Anilines

“…The azoxy, azo and hydrazo compounds as the usual side products of reduction of nitroarenes under basic conditions were not detected in the Zn-H 2 O-CO 2 reaction system. 9 At the same time, it was also noteworthy that the present method was highly chemoselective and some sensitive functional groups such as -COCH 3 , -Cl, -Br and -COOH did not undergo any change under the given reaction conditions (Table 2, Entries 3 , 4, 9, 13). No break of C-X bond was observed (Table 2, Entries 3-5) except for C-I bond, which underwent an obvious break of C-I bond and yielded 15% of aniline as a side product (Table 2, Entry 6).…”

A General Approach to Indoles: Practical Applications for the Synthesis of Highly Functionalized Pharmacophores

“…In many cases, further reduction of the N-hydroxyindole products to the corresponding indoles was competitive giving rise to multiple reaction products. Inspired by an observation of Gowda, who reported the reduction of nitro compounds to azo derivatives with Pb/triethylammonium formate (TEAF) [53], we envisioned that capture of the intermediate N-hydroxyaniline 108 by an adjacent carbonyl would provide N-hydroxyindoles 109 in a straightforward manner (Scheme 15).…”