| 87% |
With palladium diacetate; hydrazine hydrate monohydrate; potassium hydroxide In lithium hydroxide monohydrate at 50℃; for 8h; Inert atmosphere; Green chemistry; chemoselective reaction; |
2.1. The reduction of nitroarenes catalyzed by Pd NPs
General procedure: To an oven-dried reaction flask with Teflon coated stir bar purgedwith argon, Pd(OAc)2 0.01 mmol, IL4 0.08 mmol, KOH (or K2CO3)0.30 mmol, nitroarene 1 1.0 mmol and degassed HPLC grade water1.5 mL were added, and the mixture was stirred for 5 min under argonat room temperature. Then, 0.5 mL of hydrazine hydrate aqueous solution(~5.0 mmol) was syringed into the flask at the same temperature.After stirring for additional 5 min, the reaction was heat to 50 °C,and stirring for 8 h under argon. After completion, the reaction mixturewas extracted by methyl tertiary butyl ether (MTBE) (3 × 2 mL), andthe organic layer was collected and filtered through a bed of silica gellayered over Celite. The volatiles were removed in vacuo to afford theproduct 2. In some cases, further column chromatography on silica gelwas required to afford the pure desired products. |
| 85% |
With sodium tetrahydridoborate; Cupric sulfate In ethanol at 0 - 20℃; for 1h; |
2-(1H-Pyrrol-1-yl)aniline (2a)
To a solution of 1-(2-nitrophenyl)-1H-pyrrole (3.76 g, 20 mmol) inEtOH (80 mL) was added CuSO 4 ·5H 2 O (6.24 g, 25 mmol). NaBH 4 (1.51g, 40 mmol) was then added portionwise at 0 °C and the reactionmixture was stirred at room temperature for 1 h. The mixture was fil-tered through a short pad of silica gel using EtOAc (3 × 40 mL) as elu-ent. The solvent was evaporated in vacuo and the residue was sub-jected to flash chromatography (petroleum ether/EtOAc, 20:1) to af-ford 2-(1H-pyrrol-1-yl)aniline (2a). Yield: 2.69 g (85%); white crystalline solid; mp 94-95 °C.1 H NMR (400 MHz, DMSO-d 6 ): δ = 7.17-7.13 (m, 2 H), 6.83-6.78 (m, 4H), 6.34 (d, J = 2.0 Hz, 2 H), 3.53 (br s, 2 H).13 C NMR (100 MHz, DMSO-d 6 ): δ = 137.3, 123.8, 122.8, 122.4, 117.0,113.7, 111.4, 104.7. |
| 85% |
With sodium tetrahydridoborate; copper(II) sulphate In ethanol at 20℃; |
|
| 79% |
With sodium tetrahydridoborate; copper(II) sulphate In ethanol at 20℃; |
|
| 78% |
With palladium 10% on activated carbon; hydrogen In ethanol at 20℃; |
|
| 76% |
With hydrazine hydrate monohydrate In ethanol at 80℃; for 1h; Inert atmosphere; chemoselective reaction; |
2.2. Catalytic reduction of nitroarenes
General procedure: Hydrazine hydrate was chosen as the hydrogen donor for the low emission of pollutants. In a typical procedure, hydrazine hydrate (4 equiv) was added into the reactor which containing fresh prepared catalyst as described above. Then the reactor was put into a preheated oil bath with a stirring speed of 500 rpm, and the substrate (1 mmol)dissolved in 1 mL ethanol was added drop-wisely under argon. The reactions were monitored by TLC. After the reaction, the reaction mixture was vacuum filtered through a pad of silica on a glass-fritted funnel and an additional 15 mL of ethyl acetate (5 mL portions) was used to rinse the product from the silica, the filtrate was concentrated in vacuum and analyzed by GC. Products were purified by column chromatography and identified by 1H NMR and 13C NMR. |
| 76% |
With bismuth(III) chloride; sodium tetrahydridoborate In ethanol at 0 - 20℃; for 3h; |
|
| 76% |
In ethanol at 0 - 20℃; Alkaline conditions; |
1 Synthesis of Compound 4a:
N-(2-nitrophenyl)pyrrole (1.9 g, 9.90 mmol, 1.00 equiv) was weighed and dissolved in 120 ml of ethanol.And placed at 0 ° C for 30 min, then weighed the alkali slowly added to the solution, the solution changed from light yellow to black,It is accompanied by gas generation. After the reaction is stable, it is stirred at room temperature overnight.After filtration, the ethanol in the filtrate was spun dry, and the solid after spinning was extracted with ethyl acetate and brine.Drying over anhydrous magnesium sulfate and column chromatography (PE: EA = 10:1) gave white solid 4a (1.2 g, 76%). |
| 70% |
With bismuth(III) chloride; sodium tetrahydridoborate In ethanol for 2h; Ambient temperature; |
|
| 68% |
With dichloro-λ2-stannane dihydrate In ethyl acetate for 2h; Reflux; |
|
|
With bismuth(III) chloride; sodium tetrahydridoborate In ethanol |
|
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With bismuth(III) chloride; sodium tetrahydridoborate In ethanol |
|
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With bismuth(III) chloride; sodium tetrahydridoborate In ethanol |
|
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With bismuth(III) chloride; sodium tetrahydridoborate In ethanol |
|
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With bismuth(III) chloride; sodium tetrahydridoborate In ethanol |
|
|
With sodium tetrahydridoborate; copper(II) sulphate In ethanol at 20℃; |
|
|
With bismuth(III) chloride; sodium tetrahydridoborate In ethanol |
|
|
With BiCl3-NaBH4 |
|
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With bismuth(III) chloride; sodium tetrahydridoborate In ethanol at 0 - 20℃; for 3h; Inert atmosphere; |
|
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With 5%-palladium/activated carbon; hydrazine hydrate monohydrate In ethanol for 8.5h; Reflux; |
3.2.2. Synthesis of Compounds II: 2-(Piperidin-1-yl)aniline
General procedure: In an 100 mL three-necked flask equipped with a dropping funnel, 1-(2-nitrophenyl)piperidine (4.0 g)and ethanol (50 mL) were mixed and heated to reflux. Palladized charcoal (0.1 g, 5%, previously moistened with alcohol) was added. Next 80% hydrazine hydrate (15 mL) was added from a dropping funnel during 30 min. The reaction was continued for 8 h and then cooled [18,19]. The solid was filtered off and the filtrate was concentrated to give a crude product that was recrystallized from ethyl acetate and petroleum ether solution (15:1) to afford the title compound as a white powder, yield 95 % |
|
With palladium on activated charcoal; hydrazine hydrate monohydrate In ethanol for 8h; Reflux; Heating; |
3.2.2. Synthesis of 2-(Benzo[d]thiazol-2-yl)anilines 2 and 8a-8m
General procedure: In a 100 mL three-necked flask equipped with a dropping funnel, 2-(2-nitrophenyl)benzo[d]- thiazole (1, 3.0 g, 12.5 mmol) and ethanol (50 mL) were mixed and heated to reflux. Palladized charcoal (0.1 g, 5%) was added, then 80% hydrazine hydrate solution (10 mL) was added from a dropping funnel during 30 min [10,11]. The heating was continued for 8 h and then the mixture cooled. The solid was filtered off and the filtrate was concentrated to give a crude product that was recrystallized from ethyl acetate and petroleum ether solution (1:5) to afford compound 2 as a yellow powder (yield: 3.76 g, 85%). |
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With sodium tetrahydridoborate; copper(II) sulphate In ethanol at 20℃; |
|
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With ammonia hydrochloride In lithium hydroxide monohydrate for 4h; Reflux; |
|
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With ammsnium formate; zinc In methanol at 20℃; for 0.25h; |
|
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With iron(0); ammonia hydrochloride In lithium hydroxide monohydrate Reflux; |
|
|
With iron(0); ammonia hydrochloride In lithium hydroxide monohydrate at 100℃; for 4h; |
|
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With iron(0); ammonia hydrochloride In lithium hydroxide monohydrate for 4h; Reflux; |
|
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With iron(0); ammonia hydrochloride In lithium hydroxide monohydrate Reflux; |
1.2 General experimental procedures for 2-(1H-pyrrolo-1-yl)anilines
General procedure: A mixture of substituted 2-nitroanilines (1.38 g, 10 mmol, 1 equiv.) and 2, 5-dimethoxytetrahydrofuran (1.45 g, 11 mmol, 1.1 equiv.) in HOAc (30 mL) was refluxed with vigorous stirring for 1-3 hours. The reaction mixture was neutralized with aqueous NaHCO3, and then extracted with EtOAc (3×30 mL). The organic layers were combined and dried with anhydrous Na2SO4 and were evaporated under vacuum to afford a residue. Then the residue, iron powder (2.24 g, 40 mmol, 5 equiv.) and NH4Cl (0.54 g, 10 mmol, 1 equiv.) were added to water (30 mL) and refluxed for 3-8 hours. After the completion of the reaction, the mixture was extracted with EtOAc (3×30 mL). The organic layers were combined and dried with anhydrous Na2SO4, and the solvent was evaporated under vacuum to afford a residue. The residue was purified by column chromatography on silica gel to afford the target compounds. |
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