Aryl Nitro Reduction with Iron Powder or Stannous Chloride under Ultrasonic Irradiation

Abstract

The selective reduction of aryl nitro compounds in the presence of sensitive functionalities, including halide, carbonyl, nitrile and ester substituents under ultrasonic irradiation at 35 kHz is reported in yields of 39-98%. Iron powder proved superior to stannous chloride with high tolerance of sensitive functional groups and high yields of the desired aryl amines in relatively short reaction times. Simple experimental procedure and purification also make the iron reduction of aryl nitro compounds advantageous over other methods of reduction.

Synthesis and characterization of biotin derivatives as multifunctional oligosaccharide tags

“…This was attributed to the electron withdrawing nature of all three functional groups on the aromatic ring in compound 6a and 6c including the nitro group. However, the nitro group on the aromatic ring can be selectively reduced SnCl 2 38 in anhydrous ethanol without affecting the other functional groups [39][40][41][42] to produce fluorescent compounds 6b (20 mg, 0.05 mmol, 71%) and 6d (quantitative yield).…”

Effects of Ultrasound and Microwaves on Selective Reduction: Catalyst Preparation and Reactions

“…The reduction of aryl nitro compounds is known to proceed via the hydroxylamine, followed by azoxy and azo compounds, to its corresponding aryl amine after a prolonged reaction time (Scheme 6). [131] Scheme 6 Reduction of aryl nitro compounds [114] Iron powder proved superior to stannous chloride as it gave high tolerance to sensitive functional groups and high yields of the desired aryl amines in relatively short reaction times.…”

“…[114] aqueous solutions over Pd black, [116,117] CMA over Pd black and Nickel-alloy, [99] Z-2-buten-1-ol and Z-2-penten-1-ol on Pdblack, [118] and D-fructose to D-mannitol over Cu/ SiO2. [119] Several examples of selective catalytic reductions that can be improved using US are summarized in Table 2 and reviewed as follows:…”

“…[114] The sonication was performed in a US cleaning bath (35 kHz, 85 W) in an air atmosphere at 30 °C. The reduction of aryl nitro compounds is known to proceed via the hydroxylamine, followed by azoxy and azo compounds, to its corresponding aryl amine after a prolonged reaction time (Scheme 6).…”

Synthesis of reaction-ready 6,6′-biindole and 6,6′-biisatin via palladium(ii)-catalysed intramolecular C–H functionalisation

“…Thus, 8 was synthesised via a modified procedure in six steps from commercially available 2,2 0 -biphenol 3, without the need for column chromatography in an overall yield of 52% (Scheme 1). 9,10 Key was the selective nitration of 6, followed by protection of the phenolic groups to provide 7, which was further reduced under ultrasound in the presence of iron 11 to afford bianiline 8. Transition-metal-catalysed direct arylation via C-H insertion has undergone rapid development, and is still receiving significant attention.…”