Tetrahydrofuran → 2-(Dimethylamino)-1-(5-methoxy-6-nitroindolin-1-yl)ethanone

Participants

Reaction Steps

A 4-neck 22 L round bottom flask equipped with a nitrogen inlet, mechanical stirrer and thermowell was charged with chloroacetyl chloride (605 mL, 857.5 g, 7.59 mol, 2 equiv), powdered potassium carbonate (1153.7 g, 8.36 mol, 2.2 equiv) and dichloromethane (10 L). The resulting suspension was cooled by an ice bath and a solution of 5-(methyloxy)-6-nitro-2,3-dihydro-1H-indole (737 g, 3.795 moll in 4 L dichloromethane) produced in accordance with step D, immediately above, was added slowly. The reaction mixture was stirred for 2 hrs and filtered by vacuum filtration. The solid collected (a mixture of product and inorganic salts) was suspended in water (10 L) and refiltered. The solid was washed with water (3×1 L) and dichloromethane (2×1 L), dried in the oven to give 1-(chloroacetyl)-5-(methyloxy)-6-nitro-2,3-dihydro-1H-indole as a yellow solid (750 g). The filtrates from both filtrations were combined and the layers were separated. The organic layer was washed with saturated potassium carbonate solution (2×10 L) and brine (5 L), dried over sodium sulfate and evaporated in vacuo to a crude solid, which was triturated from MTBE (1 L) to afford a second crop of 1-(chloroacetyl)-5-(methyloxy)-6-nitro-2,3-dihydro-1H-indole (260 g). The combined product was 1010 g (98% yield). A 4-neck 22L round bottom flask equipped with a reflux condenser, mechanical stirrer and thermowell was charged with 1-(chloroacetyl)-5-(methyloxy)-6-nitro-2,3-dihydro-1H-indole (500 g, 1.852 mol), as described immediately above, potassium carbonate (767 g, 5.556 mol, 3 equiv), tetrahydrofuran (7.5 L) and water (3.75 L). Then dimethylamine hydrochloride salt (453 g, 5.556 mol, 3 equiv) was added as one portion. The resulting mixture was heated to reflux for 4 hrs and then allowed to cool to room temperature. Two reactions of the same size were combined. The organic solvent (THF) was removed in vacuo and the resulting suspension was filtered by vacuum filtration. The solid collected was triturated from methanol to afford N,N-dimethyl-2-[5-(methyloxy)-6-nitro-2,3-dihydro-1H-indol-1-yl]-2-oxoethanamine as a yellow solid (740 g). The mother liquor from methanol trituration was evaporated in vacuo to afford a crude solid, which was partitioned between ethyl acetate (10 L) and water (10 L). The insoluble solid was removed by filtration through Celite. The layers were separated and the organic layer was washed with brine (5 L), dried over sodium sulfate and evaporated in vacuo to afford a solid, which was triturated from heptane (2 L) to give a second crop of N,N-dimethyl-2-[5-(methyloxy)-6-nitro-2,3-dihydro-1H-indol-1-yl]-2-oxoethanamine (220 g). The combined amount of product was 960 g (93% yield). 1H NMR (400 MHz, CDCl3) δ ppm 2.59 (s, 6H), 3.24 (t, J=8.24 Hz, 2H), 3.52 (s, 2 H), 3.89 (s, 3 H), 4.19 (t, J=8.52 Hz, 2 H), 6.89 (s, 1 H), 8.60 (s, 1 H).

Provenance & Evidence