| 95.7% |
With sodium hydroxide In ethanol; water monomer Heating; |
4.1.2. Synthesis and spectroscopic characterization of chalcones
General procedure: All syntheses were carried out in the same fashion. Each reaction was monitored by TLC for 24 h to determine when the starting materials had been consumed. All TLC analyses were run on Selecto Scientific flexible silica gel-coated plates containing a fluorescent indicator and were developed using a hexanes-ethyl acetate (4:1) solution as the eluent. The following procedure is representative of the synthesis of all chalcones (see [Chart 1] and [Chart 2] for structures): A 25-mL round-bottomed flask was charged with the appropriate derivatives of both acetophenone (3 mmol) and benzaldehyde (3 mmol), and mixed with 10 mL of 95% EtOH. The mixture was then stirred magnetically while being gently heated (in a 30 °C water bath) until both starting materials dissolved. In a separate flask, NaOH (3.5 mmol) was added to 10-mL of an ethanol-water (1:1) and the mixture was stirred magnetically until the solid dissolved. The NaOH solution was then added dropwise (using a Pasteur pipet) to the ethanolic solution of acetophenone and benzaldehyde described above. In most cases, the reaction mixture turned yellow and solidified within a few minutes. Ice water (2 mL) was added to the flask and the mixture was stirred vigorously. The solid was collected on a Hirsch funnel, washed with cold water, and air-dried overnight. The purity of the crude product was determined at this point using a combination of TLC analysis, melting point measurement, and 1H NMR spectroscopy. In case of an oily product, the reaction mixture was extracted with two 10-mL portions of CH2Cl2 and the organic phase was collected, dried over Na2SO4, and removed using a rotary evaporator. The purity of the oily product was then determined as described above. All impure products (solid or oil) were purified by column chromatography using Merck Silica gel (grade 60, 230-400 mesh) and 4:1 hexanes-ethyl acetate as eluent. In case of a solid, chromatographic separation was followed by recrystallization from either methanol or ethanol-water mixture. In all cases, the purity of the final product was checked again as described above; the spectral characteristics were found to be in good general agreement with those found in the literature.4 The organic chalcones prepared for this study were either pale-yellow solids or oils of the same color (as specified); the ferrocenyl analogs were reddish-orange solids or oils. For each of the reported compounds below, the 1H NMR data is presented as δ (multiplicity, integral ratio), and the IR data as νCO, νCC. The following % yield and physical data are for new chalcones prepared for this study. Data for other chalcones (not given below) have been reported elsewhere[4], [5] and [6] and are also available online as Supplementary data. |
| 93% |
With sodium hydroxide In water monomer at 4℃; |
|
| 85% |
With sodium hydroxide In water monomer at 20℃; for 12h; |
|
| 84% |
With sodium hydroxide In water monomer at 0 - 22℃; |
|
| 78% |
With sodium hydroxide In water monomer at 0 - 25℃; for 24h; Inert atmosphere; |
|
| 72% |
With potassium hydroxide In methanol at 20℃; for 12h; |
Procedure for synthesis of chalcones containing pyridine
Referring to the literature 9b by a modified method, to a solutionof 2-acetyl pyridine (20 mmol) and aldehyde (20 mmol) in methanol (60 mL) was added to KOH (20 mmol) and H2O (2 mL) at ambient temperature. The resulting solution was stirred at room temperature for 12 h. Then H2O (1000 mL) was added,filtered under reduced the pressure, dried to obtain the crude product. The crude product was purified by column chromatography over silicagel with EtOAc/n-Hexane (1:10) as eluant, affording the chalcones containing pyridine (1a~1m). 4.1.2.1. (E)-3-Phenyl-1-(pyridin-2-yl)-prop-2-en-1-one (1a).Yellow solid, m.p. 68-70C, yield 72%; 1H NMR (500 MHz, DMSO-d6) d8.78 (d, J5.0 Hz, 1H), 8.24 (dd, J16.5, 1.5 Hz, 1H), 8.08 (d, J8.0 Hz, 1H), 8.03 (t, J7.5 Hz, 1H), 7.83 (d, J16.5 Hz, 1H), 7.79(t, J2.5 Hz, 1H), 7.69 (t, J6.0 Hz, 1H), 7.45 (t, J2.5 Hz, 3H); 13CNMR (126 MHz, DMSO-d6) d189.18 (s), 153.94 (s), 149.66 (s), 144.49(s), 138.19 (s), 135.14 (s), 131.31 (s), 129.58 (s), 129.24 (s), 129.10 (s),122.99 (s), 121.35 (s). |
| 60% |
With sodium hydroxide at 20℃; for 8h; |
|
| 21% |
With sodium hydroxide In ethanol for 24h; Ambient temperature; |
|
|
With sodium hydroxide |
|
|
With potassium hydroxide In ethanol for 2h; Ambient temperature; |
|
|
With potassium hydroxide In methanol |
|
|
With sodium hydroxide |
|
|
With base |
|
|
With diethylamine In propan-1-ol for 12h; Reflux; |
|
|
With potassium hydroxide In ethanol; water monomer at 20℃; |
|
|
With sodium hydroxide In methanol; water monomer at 0 - 20℃; |
|
|
With potassium hydroxide In methanol at 20℃; for 2h; |
|
|
With sodium hydroxide In water monomer at 20℃; |
|
|
Stage #1: 2-acetylpyridine; benzaldehyde In water monomer at 4℃; for 0.5h;
Stage #2: With sodium hydroxide In water monomer at 4℃; for 0.5h; |
|
|
With sodium hydroxide In methanol; ethanol at 5 - 20℃; |
4.1.2. General method for synthesis of chalcones (6a-e) and (7a-c)
General procedure: Equimolar portions of the appropriately substituted aryl aldehydes(10 mmol) and ketones (10 mmol, 1equiv) were dissolved in approximately 25 mL of ethanol. The mixture was allowed to stir for 30 min at5-10 °C. 1 mL aliquot of a 10% methanolic sodium hydroxide solution was added dropwise to the reaction mixture. The reaction solution was allowed to stir at room temperature for approximately 4-10 h. Progress of the reaction was monitored via TLC. After completion of the reaction,excess of solvent was evaporated from the mixture using rotary evaporator.Chilled water was poured into the reaction mixture and precipitatesof intermediate chalcones were filtered and dried. The crude product was then recrystallized from ethanol to get pure chalcones. |
|
With sodium hydroxide In water monomer at 20℃; |
|
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