| 76% |
With nitric acid In nitromethane for 2h; |
1 Step 1: Preparation of 6-amino-3,4-methylenedioxyacetophenone:
3,4-methylenedioxyacetophenone was dissolved in nitromethane (80mL), and concentrated nitric acid (20.7niL) was added dropwise to it. The mixture reacted for 2 hr and saturated sodium bicarbonate solution was added dropwise to it to get the pH to about 7. The mixture was extracted with dichloromefhane for 3 times. The organic layer was combined washed with brine, dried by anhydrous MgSCri and concentrated. The yellow oil resultant was purified by column chromatography(ethyl acetate; petroleum ethei=l : 8) and resulted in 7.8 g light yellow solid (76%). nip 110-112 e C |
| 58% |
With nitric acid; acetic acid In water at 0 - 40℃; for 4.5h; Inert atmosphere; |
4',5'-Methylenedioxy-2'-nitroacetophenone (4b)
Following a slightly modified procedure described by McGall et al50, a solution of 3', 4'- (methylenedioxy)acetophenone 4a (16.416 g, 0.1 mol) in glacial CH3COOH (64 mL) was added drop-wise to a 2 litre three-necked round-bottomed flask containing cone. HN03 (136 mL, 70% strength) at o°C over 1 h. The reaction mixture was maintained at o°C during addition and for a further 1 h with stirring under an argon atmosphere. The mixture was then warmed to 40 °C and stirred for additional 2.5 h. Finally, the mixture was cooled to r.t. and poured slowly into crushed ice (1 litre) in a beaker. A yellow precipitate appeared which was stirred for 15 min and then filtered. The yellow solid was washed with water (3 x 200 mL) and dried in vacuum. The crude yellow solid was then purified by recrystallization (THF/n-hexane) and then by flash chromatography on Si02 [eluent: CH2Cl2/n-hexane (1:1) to ioo%CH2Cl2] to obtain 4',5'-methylenedioxy- 2'-nitroacetophenone32’50’51 4b as yellow crystals (12.141 g, 58%): R/= 0.52 (CH2Cl2); m.p. 122.8-124.O °C(51 m.p. 112 °C); NMR (400.13 MHz, CDCl3) £2.45 (s, 3H), 6.16 (s, 2H), 6.71 (s, lH), 7.48 (s, lH); 13C NMR (100.61 MHz, CDCl3) £30.2 (CH3), 103.8 (CH2), 104.8 (CH), 106.2 (CH), 135.1 (C), 140.1 (C), 148.9 (C), 152.8 (C), 199.3 (C); IR (CH2Cl2) Vmax 2980, 1708, 1525, 1506, I484, 1424, 1362, 1338, 1271, 1152, 1038, 932, 875, 819 cm 1; MS (ESI+) m/z (rel intensity) 232 [(M+Na)+, 10%], 210 (2), 209 (7), 194 (100), 171 (45), 130 (32), 111 (9)· |
| 36% |
With trifluoroacetic acid; sodium nitrite for 20h; |
1 Step 1; Synthesis of 1-(4,5-(methylenedioxy)-2-nitrophenyl)ethanone
<> 3,4-(Methylenedioxy)acetophenone (5.04 g, 30.7 mmol) was put into a 200 mL two-necked eggplant flask to be dissolved in trifluoroacetic acid (50 mL), sodium nitrite (6.30 g, 91.4 mmol) was gradually added thereto, and the solution was stirred for 20 hours. Pure water (100 mL) was added thereto for extraction using dichloromethane (100 mL*3), and the organic layer was washed with saturated saline solution (100 mL*3), dried over anhydrous magnesium sulfate, filtered, and concentrated. The resultant was purified by silica gel column chromatography (hexane:ethyl acetate=4:1), thereby obtaining 2.35 g (11.2 mmol, 36%) of a yellow solid (intermediate compound 21; 1-(4,5-(methylenedioxy)-2-nitrophenyl)ethanone). The identification result of the obtained intermediate compound 21 is described below. 1H NMR (CDCl3/TMS, 400 MHz): δ 2.49 (3H, s), 6.18 (2H, s), 6.75 (1H, s), 7.55 (1H, s). |
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