Synthesis of chloroanilines: selective hydrogenation of the nitro in chloronitrobenzenes over zirconia-supported gold catalyst

Abstract

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Copper‐Catalyzed Oxybromination and Oxychlorination of Primary Aromatic Amines Using LiBr or LiCl and Molecular Oxygen

“…[22][23][24] Under atmospheric pressure, high yields of monobrominated aromatics were achieved with hydrobromic acid, from which molecular bromine was generated in situ using sodium nitrite [25] or a P-Mo-V heteropoly acid [20] as catalyst. Recently, oxychlorination and oxybromination of phenylpyridines giving mono-and dihalogenated products under one atmosphere of dioxygen have been reported; however, the method involves the use of X 2 CHCHX 2 (X = Cl, Br) as a halogen source and CuA C H T U N G T R E N N U N G (OAc) 2 as the catalyst in the case of oxychlorination and as a stoichiometric reagent in the case of oxybromination. [26] In the only work found in the literature which describes oxychlorination and oxybromination of aniline with dioxygen, tert-butyl hydroperoxide was added as initiator.…”

“…[12][13][14][15][16][17][18][19][20] As far as chloro-A C H T U N G T R E N N U N G anilines are concerned, they are usually produced by the hydrogenation of corresponding chloronitrobenzenes; however, this process is heavily complicated by a concomitant hydrodechlorination reaction so that it still remains a big challenge to leave intact carbonchlorine bonds and selectively reduce a nitro group in the same molecule. [2,5,21] In oxidative halogenation, halide ions can be used as a halogen source together with a suitable oxidant; thus, this method represents more ecologically benign and economically attractive pathway to haloaromatics than classical electrophilic substitutions. Main advantages of oxyhalogenation, which make it safer and greener, are the use of low value and easy to handle metal halides as halogenating agents and atom economy, i.e., a full utilization of halogen atoms instead of using only half of the available amount.…”

“…[1, 2,3] Bromoaromatics are particularly versatile synthetic starting materials due to the possibility of their use in carbon-carbon bond formation reactions via Heck, Stille and Suzuki transmetallation processes. [4] Aromatic haloamines are used for the manufacture of polyurethanes, rubber chemicals, agricultural products and drugs.…”

A Green Reduction of Aromatic Nitro Compounds to Aromatic Amines Over a Novel Ni/SiO2 Catalyst Passivated with a Gas Mixture

“…The important developed catalytic systems are listed as follows, MCM-41-silylamine palladium(II)/THF [5],poly(4-vinylpyridine-co-N-vinylpyrrolidone)-Pd (0)/EtOH [6], Au/SiO 2 /EtOH [7], nanosized nickel/EtOH [8], Au-Pt-NH 2 -Si-MCM-41/CH 3 OH [9], Au/Al 2 O 3 [10], silica sol-gel encaged Pd-[Rh(cod) Cl] 2 /n-heptane [11], nanosized NiCoB amorphous alloy/ CH 3 OH [12], PSF-Pd/DMF [13], Ni/SiO 2 [14], PVPA-Pd/ EtOH/KOH [15], zero-valent iron powder/CH 3 CN/phosphate buffer [16], Au/TiO 2 or Au/Fe 2 O 3 [17,18], Cocolliod or NiPd-colliod/THF [19], Au/ZrO 2 /EtOH [20], LaMO 3 /KOH/propan-2-ol [21], La 1-x Sr x FeO 3 /KOH/propan-2-ol [22], Co(II)/mesoporous aluminophosphate/KOH/ iPrOH [23], Ni-MCM-41/iPrOH/KOH [24], hydrazine hydrate/ferrihydrite/EtOH [25], Polymer-Supported Formate and Magnesium/MeOH [26], Polymer-Supported Formate/Pd-C/ MeOH [27], CeO 2 -SnO 2 /hydraine/MeOH [28], Heteropolyacid/MeOH/N 2 H 4 [29], RhCl 3 /CO/H 2 O [30], Ru 3 (CO) 12 [49]. However, some difficulties is still existed, such as (1) seriously environmental pollution from residue, (2) expensive or sensitive to air, (3) significant limitations based on safety and handling considerations, (4) strong acidic or alkaline media, (5) the reaction conditions of most of these methods can destroy many sensitive functional groups.…”

“…Nowadays, numerous methods for the reduction of aromatic nitro have been reported in the literatures, such as catalytic hydrogenation [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], catalytic transfer hydrogenation [21][22][23][24][25][26][27][28][29], CO/H 2 O conditions [30][31][32] and other reduction systems [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. The important developed catalytic systems are listed as follows, MCM-41-silylamine palladium(II)/THF [5],poly(4-vinylpyridine-co-N-vinylpyrrolidone)-Pd (0)/EtOH [6], Au/SiO 2 /EtOH [7], nanosized nickel/EtOH [8], Au-Pt-NH 2 -Si-MCM-41/CH 3 O...…”