Indium as a Reducing Agent: Reduction of Aromatic Nitro Groups

Moody, Christopher J.; Pitts, Michael R.

doi:10.1055/s-1998-1837

Cited by 87 publications

(24 citation statements)

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“…A selective reduction of nitro arenes to aromatic amines was achieved by using In metal as the reducing reagent. Thus, treatment of a range of aromatic nitro compounds with In powder in aqueous ethanolic ammonium chloride resulted in selective reduction of the nitro group, other substituents such as ester, nitrile, amide, carboxylic acid and halide groups remaining unaffected [38] . More recently, N -aryl acetamides were prepared in excellent yields from nitroarenes in the presence of acetic anhydride, acetic acid and In in a one -pot procedure.…”

Section: Reduction Of Nitro Compoundsmentioning

confidence: 99%

Dissolving Metals

Yus

Foubelo

2008

Modern Reduction Methods

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17 IntroductionDissolving metals have been used extensively as reducing agents for more than a century but today they have been partially displaced from the central fi eld of organic synthesis by the use of other more selective methodologies, such as metal hydrides [1] and catalytic hydrogenations [2] . However, dissolving metals are still of interest for the selective reduction of specifi c polar functional groups (such as hindered cyclic ketones) and the reductive cleavage of some activated bonds [3] .Regarding the mode of action of electropositive metals in reduction processes, it is generally assumed that an initial single -electron transfer ( SET ) from the metal to the organic substrate takes place to give a radical anion [4] . Depending on the organic substrate and on the reaction conditions (mostly on the solvent), the highly reactive resulting radical anion can then decompose via a number of different routes. For instance, for compounds (I) with multiple C = X bonds (X = CR 2 , O, NR, S), the radical anion (II) could be protonated in the presence of a proton source (the solvent) to give a new radical (III) , which after a further SET from the metal, and further protonation of the resulting anion (IV) , would lead to the reduced product (V) . In the absence of a proton source, coupling of two radical anions (II) can occur to give fi rst the dianionic species (VI) and, after hydrolysis, compounds of type (VII) . Organic substrates (VIII) with activated bonds X − Y (X = CR 3 , OR, SR, NR 2 ; Y = CR 3 , OR, SR, NR 2 , Hal (F, Cl, Br, I)) also undergo reductive cleavage by means of electropositive metals through a SET mechanism. In this case, the initially formed radical anion (IX) suffers the activated X − Y bond scission to generate a radical (X) and an anion (XI) . Radical (X) would be converted to an anion after a new electron transfer from the metal, and fi nal protonation would yield the corresponding reduced products (XII) and (XIII) , respectively (Scheme 17.1 ).Most of the reductions by means of dissolving metals have been performed using highly electropositive metals, such as Li, Na and K, in liquid NH 3 as solvent. Less electropositive metals (Mg, Ca, Sr, Ba, Ni, Cu, Zn, In, Sn, Pb) have also been used, so by choosing the appropriate metal, solvent and cosolvent it is possible to

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Section: Reduction Of Nitro Compoundsmentioning

confidence: 99%

Dissolving Metals

Yus

Foubelo

2008

Modern Reduction Methods

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“…Among the first to systematically investigate the reaction of aromatic nitro groups with indium were Moody and Pitts who reported the reduction of the nitro functionality in several substituted nitrobenzenes (Scheme 39), in 6-nitroquinoline and in 5-nitroisoquinoline. 138…”

Section: Reduction Of Aliphatic and Aromatic Nitro Groupsmentioning

confidence: 99%

Indium in Organic Synthesis

Podlech¹,

Maier²

2003

Synthesis

245

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“…Reduction of nitroaromatic compounds by catalytic hydrogenation11–15 is probably one of the best‐known methods to produce aromatic amines, although various synthetic methods have appeared in the literature 16, 17. Many novel reducing agents have been reported in the literature, such as the AlNiCl 2 THF system,18 decaborane in methanol,19 indium–ammonium chloride in ethanol,20 hydrazine hydrate/ferric oxide–magnesium oxide, N , N ‐dimethyl‐hydrazine in the presence of catalytic FeCl 3 .6H 2 O in methanol,21, 22 diethyl chlorophosphite,23 samarium iodine in methanol24 and water‐soluble palladium catalyst25 for the preparation of aromatic amines.…”

Section: Introductionmentioning

confidence: 99%