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General procedure: Phosphorus oxychloride (0.42 g, 2.74 mmol) was added dropwise to a solution of the indole 5b, 5e-5g (0.30 g, 2.29 mmol) in DMF (0.84 g, 11.4 mmol) at 0 C for 30 min. The solution was then heated at 40 C for 1 h. Ice was added to the reaction vessel, followed by a solution of sodium hydroxide (2 M). The solution was refluxed for 40 min. The mixture was cooled and extracted using ethyl acetate, and the organic phase was washed with brine. The organic extracts were combined, dried over Na2SO4, and concentrated. The crude residue was purified by chromatography on a silica gel column using hexane-ethyl acetate as an eluent to obtain the desired product [19].
77%
General procedure: Into a 25 mL tube, Ph3P (0.75 mmol, 1.5 equiv.), ICH2CH2I (0.75 mmol, 1.5 equiv.)indoles 1 (0.5 mmol, 1 equiv.), DMAP (0.5 mmol, 1 equiv.), and DMF (2 mL) wereadded under air atmosphere. The resulting mixture was stirred at 80 oC for 2 hours. H2O(5 mL) was added and stirred at 80 oC for another 2 hours. The mixture was cooled toroom temperature. A saturated aqueous brine solution was added, and the crude organicproduct was extracted by CH2Cl2. The combined organic phase was dried withanhydrous Na2SO4. After filtration, the solution was concentrated under reducedpressure to remove the solvent. The residue was subjected to flash columnchromatography on silica gel (pentane/ethyl acetate) to give the pure pro ducts 4j-4u.
48.27%
The starting reagent, 5-iodoindole-3-carboxaldehyde was prepared. Dimethylformamide (0.3602 g, 4.93 mmol) was reacted with phosphorus oxychloride (0.1908 g, 1.24 mmol) at 0 C. for 30 mm to produce an electrophilic iminium cation. After that 5-iodoin- dole (0.2978 g, 1.23 mmol) in DMF was added dropwise and stirred in an ice bath for 3 h. The reaction mixture was poured into ice-water, neutralized with iN NaOH, and lefi it overnight. Then, it was extracted with CH2C12, dried with MgSO4 anhydrous, and concentrated in vacuo before purification (50% EtOAc in hexane) to obtain orange solid (48.27%). Afier that the terminal alkyne product was prepared with the method described above and purified by column chromatography (20% EtOAc in hexane to EtOAc) to yield brown solid compound (38.21% over all steps). ‘H-NMR (400 MHz, CD3OD) ? 9.89 (s, 1H), 8.29 (s, 1H), 8.14 (s, 1H), 7.44 (d, J=8.4 Hz, 1H), 7.36 (d, J=8.5 Hz, 1H),3.38 (s, 1H).
General procedure: Phosphorous oxychloride (2 mmol) was added dropwise to dimethylformamide (3 mL) cooled under ice-bath and allowed to stir for 30 min. A solution of indoles 4a-4h or azaindole 5 (1 mmol) in DMF (5 mL) was added dropwise for 5 min at 0 oC. The mixture was further allowed to stir for 3 h at 90-100 oC. Reaction mixture was cooled to room temperature and poured into crushed ice. Excess POCl3 was quenched with 1 N NaOH and left overnight at room temperature. Ice-cold reaction mixture was then extracted (50 mL × 3) with EtOAc. Combined organic layer was concentrated on rotary evaporator and crude products were purified by silica gel (No.100-200) column chromatography to get indole-3-carboxaldehydes 1a-1h or 6 in 60-80% yield.
General procedure: Phosphorus oxychloride (0.86 mL) was added dropwise to dimethylformamide (1.0 mL) with ice-bath cooling. The chosen indoles (1.0 g) were added as a dimethylformamide solution for preparation of corresponding indolecarbaldehydes. The resulting mixture was stirred at room temperature for one hour. The reaction mixture was quenched with chilled water, followed by the addition of aq Sodium hydroxide solution and refluxed at 100 C for 15 min. The reaction mixture was cooled to room temperature and maintained at 0 C overnight. The precipitates formed were collected and washed with water. After this, the -NH groups of different indolecarbaldehydes were protected with methyl, tosyl, benzyl, or methylsulfonyl by using corresponding halogenides (1.5 equiv) under different basic conditions, such as sodium hydride (1.5 equiv) using acetonitrile as a solvent. Then, the reaction of resulting N-protected indolecarbaldehydes (1.0 g) with nitromethane (5 mL) in the presence of 30 mol % of ammonium acetate as the catalyst to furnish the desired indolylnitroalkenes.9
With trichlorophosphate; at 0 - 60℃; for 6.5h;
General procedure: A solution of indole (1.71 mmol) in dimethyl formamide (1 ml) was added to a cooled solutionof trichlorophosphate (1.88 mmol) in dimethyl formamide (1 ml) and stirred at room temperature for30 min and allowed to stir for 6 h at 60 C. The reaction mixture was allowed for cooling and pouredinto ice-cold water and added dropwise to an ice-cold solution of 2M NaOH. The suspension wasextracted with ethylacetate, the combined organic extract was concentrated to dryness to yield desiredindole-3-carboxaldehyde.
With perchloric acid adsorbed on silica gel; anthranilic acid amide; In acetonitrile; at 80℃; for 6h;
General procedure: Solid acid catalyst (50% w/w) was added to the solution of indole-3-carboxaldehydes 1a-1h or azaindole-3-carboxaldehyde 6 (1 mmol) and anthranilamide 2a (1 mmol) in acetonitrile (6 mL). The reaction mixture was allowed to stir for 6-24 h at room temperature or at reflux temperature. The progress of the reaction was monitored by TLC. After completion of the reaction, it was allowed to cool and catalyst was recovered by filtration. The filtrate was concentrated to get crude products which after silica gel (No.100-200) column chromatography gave deformylated products 4a-4h or 5 in 25-90% yield.
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