Go Nitro: To Stand Divided: 2

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b) C. Feng, H. Zhang, N. Shang, S. Gao and C. Wang, Chin. Chem. Lett., 2013, 24, 539 CrossRef CAS PubMed; Reduction of aromatic nitro compounds to anilines in THF–water mixture at r.t. using Mn as reducing agent and CuCl 2 as catalyst was reported by Sarmah and Dutta. 96 Nitro group was selectively reduced to NH 2 in the presence of OH, NH 2, Cl, COOH, ester and CN with 75–88% yield. The products were isolated in pure form by simple acid–base treatment. Similarly Yoo et al. have shown that the NbCl 5/In system mediates an efficient and mild reduction of aromatic nitro compounds to the corresponding amines. 97 The Br, Cl, COOCH 3 and COCH 3 functionalities remained unaffected.

Multiwalled carbon nanotubes were functionalized with small organic molecules containing specific ketonic carbonyl groups through noncovalent van der Waals and π–π interactions and utilized as metal-free catalysts for reduction of nitroarenes. 76a Boron-doped pyrolytic graphene oxide was synthesized and explored for efficient reduction of nitrobenzene to aniline. 76b However, selectivity studies with this catalytic system were not undertaken. Reduced graphene oxide was also explored as a catalyst for hydrogenation of nitrobenzene. 76cRu and Ir catalysts, which are not particularly selective under the conditions of conventional hydrogenation carried out with molecular hydrogen, when used in the aqueous-phase reforming/hydrogenation (APR/Hyd) process, become >99.9% selective for hydrogenation of o-CNB to o-chloroaniline. 80,81 Pyridyl)phenylmethanol was used as hydrogen donor for reduction of aromatic nitro compounds to arylamines. These were subsequently subjected to conjugate addition through aza-Michael reaction in a one-pot manner. 102

Dumbbell- and flower-like Au–Fe 3O 4 heterostructures have been fabricated by thermal decomposition of an iron oleate complex in the presence of Au NPs using different sizes of Au NPs as the seeds and employed as magnetically recyclable catalysts (for p-nitrophenol and 2,4-dinitrophenol reduction) by Lin and Doong. 39a Similarly, Cu( II) NPs on silica Fe 3O 4 support were used for reduction of nitroarenes with NaBH 4 in aqueous medium at r.t. by Sharma et al. 39b Other reducible moieties like CN and halides were retained during reduction. a) S. Harish, J. Mathiyarasu, K. L. N. Phani and V. Yegnaraman, Catal. Lett., 2009, 128, 197 CrossRef CAS; Plant cells from a grape ( Vitis vinifera L.) reducing aromatic nitro compounds under mild conditions to the corresponding hydroxylamines was observed by Li et al. 115 The chemical community had ignored gold due to its low reactivity, but recently its unique catalytic properties have drawn the attention of numerous research groups, which has been reflected in a number of research publications in the literature.Pd( II) phthalocyanine was also used with low catalyst loading up to 1 mol% along with NaBH 4 in EtOH by Verma et al. 38 a) R. Kaur, C. Giordano, M. Gradzielski and S. K. Mehta, Chem.–Asian J., 2014, 9, 189 CrossRef CAS PubMed; c) B. B. Lohray, S. Baskaran, B. S. Rao, B. Y. Reddy and I. N. Rao, Tetrahedron Lett., 1999, 40, 4855 CrossRef CAS. On the desktop or web client (this is not available on mobile), go to User Settings > Subscriptions. Soundboard anywhere: Use any Soundboard from a server you’re in, anywhere you have permissions to use them in.

The discussion is organized with respect to the use of reducing agents such as molecular H 2, hydrides, hydrazine, in situ H 2 generation, metal reductants, redox systems, light-induced electron transfer and biotic reduction in benign, clean, non-hazardous and non-polluting processes for reduction of nitroarenes. Chaudret et al. have described the chemoselective reduction of a series of functionalized nitroarenes with H 2 gas (1 bar) at r.t. using Pt NPs stabilized with N-heterocyclic ligands as catalyst. 22 Sensitive functionalities such as carbonyl, olefins as well as halogens were tolerated in this reduction. Ethyl-4-nitrocinnamate was reduced with 79% selectivity, 4-chloronitrobenzene with 95%, 4-nitrobenzaldehyde with 94% and 3-nitropyridine with >99%. Vogt PF, Gerulis JJ (2000) Ullmann’s encyclopedia of industrial chemistry. Wiley-VCH, Weinheim, Germanyb) D. Cantillo, M. M. Moghaddam and C. O. Kappe, J. Org. Chem., 2013, 78, 4530 CrossRef CAS PubMed. I. Sorribes, G. Wienhofer, C. Vicent, K. Junge, R. Llusar and M. Beller, Angew. Chem., Int. Ed., 2012, 51, 7794 CrossRef CAS PubMed.

a) J. F. Quinn, C. E. Bryant, K. C. Golden and B. T. Gregg, Tetrahedron Lett., 2010, 51, 786 CrossRef CAS PubMed; Palladium NPs immobilized on carbon nanospheres are reported to catalyze reduction of nitroaromatic compounds with 1.36% Pd using hydrazine hydrate in ethanol–water mixture as described by Yu et al. 63a The authors claim that they could selectively reduce the nitro group in the presence of other reducible vinyl and aldehyde groups. It may be noted that no hydrazone product or the alcohol product is reported though hydrazine was used in excess (1 : 10 molar ratio). The low Pd loading (1.36%) also helped to retain halogen in the reduced products. In the case of 3-nitrophenol and 4-methylnitrobenzene, the main byproducts were corresponding azo and azoxy intermediates. Similarly Pd/C was also studied for selective reduction of halogenated nitrobenzenes using hydrazine hydrate under reflux or microwave (MW) conditions by Li and coworkers. 63b a) L. Pehlivan, E. Métay, S. Laval, W. Dayoub, P. Demonchaux, G. Mignani and M. Lemaire, Tetrahedron Lett., 2010, 51, 1939 CrossRef CAS PubMed; Ionic liquids (IL) are pursued as green alternatives for toxic volatile solvents. IL-like copolymer stabilized Pt nanocatalysts were studied for selective hydrogenation of 2,4-dichloro-3-nitrophenol to 2,4-dichloro-3-aminophenol using H 2 gas in different IL by Yuan et al. 23 The IL system containing an alcohol group displayed better selectivity, recyclability (9 times) and higher turnover number (2075). X. Yuan, N. Yan, C. Xiao, C. Li, Z. Fei, Z. Cai, Y. Kou and P. J. Dyson, Green Chem., 2010, 12, 228 RSC.c) J. W. Larsen, M. Freund, K. Y. Kim, M. Sidovar and J. L. Stuart, Carbon, 2000, 38, 655 CrossRef CAS.