Electrosynthesis of Azobenzenes Directly from Nitrobenzenes

Abstract

Main observation and conclusion The electrochemical reduction strategy of nitrobenzenes is developed. The chemistry occurs under ambient conditions. The protocol uses inert electrodes and the solvent, DMSO, plays a dual role as a reducing agent. Its synthetic value has been demonstrated by the highly efficient synthesis of symmetric, unsymmetric and cyclic azo compounds.

A Green and Efficient Synthesis Method of Benzo[c]cinnolines: Electrochemical Reduction of 2,2’‐Dinitrobiphenyl in the Presence of CO2

“…Bulk electrolysis was performed at −1.841 V(vs Fc/Fc + ), or −1.541 V(vs Fc/Fc + ). The electrolytic products (Benzo[c]cinnolines, benzo[c]cinnoline‐N‐oxide) are generated in the cathode chamber, while the DMSO oxidation occurs in the anode [25] . The electrolytic products were detected by HPLC (Agilent 1100) equipped with a Qualisil BDS C‐18 column (250 mm×4.6 mm, 5 μm), at λ=254 nm.…”

“…The electrolytic products (Benzo[c]cinnolines, benzo[c]cinnoline-N-oxide) are generated in the cathode chamber, while the DMSO oxidation occurs in the anode. [25] The electrolytic products were detected by HPLC (Agilent 1100) equipped with a Qualisil BDS C-18 column (250 mm × 4.6 mm, 5 μm), at λ = 254 nm. The mobile phase was a mixture of acetonitrile: 0.05 % phosphoric acid solution at the ratio of 70 : 30 (V/V), with flow rate 1 mL/min.…”

Organocatalytic Reduction of Aromatic Nitro Compounds: The Use of Solid-Supported Phenyl(2-quinolyl)methanol

“…By keeping the hydrazo compound obtained from 3-nitrobenzonitrile ( 7l ) (0.037 g) in an oxygen atmosphere for 18 days, the diazene 10l (0.027 g, 93%) was isolated as the sole reaction product. 39 …”

“…By heating 4-nitrobenzaldehyde ( 7q ) (0.038 g) for 24 h, a mixture (ratio 1:2, 1 H NMR) of 1,2-bis­(4-hydroxymethylphenyl)­diazene ( 10q ) , and 1,2-bis­(4-hydroxymethylphenyl)­hydrazine ( 11q ) (0.026 g, 85%) was recovered. 1 H NMR (CDCl 3 ) δ: [7.91 (d, J = 8.0 Hz, 4H)], [7.51 (d, J = 8.1 Hz, 4H)], 7.21 (d, J = 8.3 Hz, 4H), 6.83 (d, J = 8.0 Hz, 4H), 5.66 (br s, 2H), [4.79 (s, 4H)], 4.57 (s, 4H)…”

“…From 4-nitrobenzaldehyde ( 7q ) (0.038 g), after 2 h of stirring under an O 2 atmosphere, 10q (0.026 g, 86%) was recovered. , 1 H NMR (CD 3 OD) δ: 7.89 (d, J = 8.4 Hz, 4H), 7.53 (d, J = 8.5 Hz, 4H), 4.69 (s, 4H). 13 C NMR (CD 3 OD) δ: 151.8 (s), 144.8 (s), 127.1 (d), 122.4 (d), 63.2 (t).…”