100% |
With N-ethyl-N,N-diisopropylamine; In 1,4-dioxane; for 0.666667h;Reflux;Product distribution / selectivity; |
A solution of 2-nitrobenzene-1,4-diamine (2.00 g; 13.1 mmol), di-tert-butyl dicarbonate (3.14 g, 14.4 mmol), and DIPEA (2.6 mL; 14.9 mmol) in dioxane (40 mL) was heated at reflux for 40 min, then allowed to cool to room temperature. The mixture was concentrated under reduced pressure and taken up in EA (100 mL). The EA solution was washed with water and the aqueous phase extracted with EA. The combined organic layers were washed with saturated aqueous sodium bicarbonate and brine, dried over magnesium sulfate, and concentrated under reduced pressure to give tert-butyl 3-amino-4-nitrophenylcarbamate in quantitative yield as a brown solid. To a stirred solution of tert-butyl 3-amino-4-nitrophenylcarbamate (2.74 g; 10.8 mmol) in anhydrous THF (50 mL) was added sodium hydride (0.868 g of a 60 wt % dispersion in oil, 21.7 mmol) in portions over 10 min. The mixture was stirred for a further 5 min at room temperature and then iodoethane (950 muL; 11.9 mmol) was added. The solution was stirred for 20 hr, water (1 mL) was added, and the solution concentrated under reduced pressure. The residue was partitioned between EA and water and the phases separated. The aqueous phase was extracted twice with EA and the combined organic phases washed with water, saturated aqueous sodium bicarbonate and brine. The organic solution was dried over magnesium sulfate and concentrated under reduced pressure to give a mixture of mono- and di-ethylated products (2.18 g). This was purified by silica gel column chromatography eluting with 1:4 EA/hexanes to give tert-butyl 4-amino-3-nitrophenyl(ethyl)carbamate (0.534 g) as an orange solid. A solution of tert-butyl 4-amino-3-nitrophenyl(ethyl)carbamate (0.514 g; 1.83 mmol) in 4M hydrogen chloride in dioxane (10 mL) was stirred at ambient temperature for 3 hr. The solvent was removed under reduced pressure and the residue dissolved in water. The pH was adjusted to 10 with 1M aqueous sodium hydroxide and the aqueous phase was extracted three times with EA. The combined organic extracts were washed with brine, dried over magnesium sulfate, and concentrated under reduced pressure to give N1-ethyl-3-nitrobenzene-1,4-diamine (0.311 g) as a purple solid. N1-Ethyl-3-nitrobenzene-1,4-diamine (0.208 g; 1.38 mmol) was dissolved in acetonitrile (10 mL) and N,N-diethylglycine sodium salt (0.192 g; 1.25 mmol) and DEPBT (0.375 g; 1.25 mmol) were added, followed by triethylamine (577 muL; 4.14 mmol). The mixture was stirred at room temperature for 8 hr; and then further quantities of N,N-diethylglycine sodium salt (0.192 g; 1.25 mmol), DEPBT (0.375 g; 1.25 mmol), and triethylamine (577 muL; 4.14 mmol) were added and stirring continued for 63 hr. Solids were removed by filtration and the filtrate concentrated under reduced pressure. Water was added to the residue and the pH was adjusted to 10 with saturated aqueous sodium bicarbonate. This solution was extracted three times with EA, and the organic extracts combined, washed with water and brine, dried over magnesium sulfate, and concentrated under reduced pressure to give N-(4-amino-3-nitrophenyl)-2-(diethylamino)-N-ethylacetamide (0.303 g) as a brown oil. A solution of N-(4-amino-3-nitrophenyl)-2-(diethylamino)-N-ethylacetamide (0.092 g; 0.31 mmol) in ethanol (5 mL) was hydrogenated at atmospheric pressure with 10% palladium on carbon (11 mg) at room temperature for 22 hr. The mixture was filtered through diatomaceous earth, washing with ethanol, and the filtrate was concentrated under reduced pressure to give N-(3,4-diaminophenyl)-2-(diethylamino)-N-ethylacetamide in quantitative yield as a brown oil. |
80% |
In tetrahydrofuran; for 2h;Heating / reflux; |
To a refluxing solution OF 2-NITRO-1, 4-DIAMINOBENZENE (10.135 g, 66.18 mmol) in tetrahydrofuran (100 mL) Boc20 (DI-TERT-BUTYL dicarbonate, 32.6 g, 149 mmol) was added by portions during 2 hours. The obtained solution was poured into heptane (2 L), sonicated for 15 minutes, filtered and dried in vacu to furnish 13.40 g of the title compound as a red solid. Yield 80%. |
|
In tert-butyl alcohol; at 40℃; for 1h; |
A solution OF 2-NITRO-BENZENE-1, 4-diamine (1-1,1. 01 g, 6.53 mol) in tert-butanol (20 mL) was treated with di-tert-butyl dicarbonate (1.42 g, 6.53 mol) and heated at 40C. After lh stirring at the same temperature, the reaction mixture was cooled to the ambient temperature and concentrated in vacuo. The resulting crude mixture was dissolved in ethyl acetate, treated with active carbon, and filtered though a pad of Celite (3 g). The filtrate solution was concentrated in vacuo to afford the desired product as a deep orange powder. The intermediate (1-2) was dissolved in methanol (20 mL) and mixed with palladium on carbon (10%, 50 mg). Hydrogen gas was bubbled into the reaction mixture at the ambient temperature for LH. Any insoluble material was removed by filtration and the filtrate solution was concentrated in vacuo. The resulting crude product was triturated with ethyl acetate (10 mL) and hexanes (2 mL) to give (4- Amino-3-nitro-phenyl) -carbamic acid tert-butyl ester (1-3) as a pale gray solid. The product was stored at-15 OC in a brown bottle ; 1H NMR (500 MHz, DMSO-d6) 8 8.82 (s, 1 H), 6.84 (s, 1 H), 6.56 (d, 1 H, J = 8.5 Hz), 6.49 (d, 1 H, J = 8.0 Hz), 5.71 (bs, 4 H). |