Method for preparing chloramphenicol
A technology of chloramphenicol and structural formula, applied in the field of compound preparation, can solve the problems of increased production cost, three wastes, long synthetic route of chloramphenicol, etc., and achieves the effects of cost reduction, low raw material price and high total yield
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Embodiment 1
[0034] 1 of the preparation of embodiment 1 (R)-2-nitro-1-phenylethanol
[0035] 0.9 g copper trifluoromethanesulfonate Cu(OTf) 2 (0.25mmol), 1.2 grams of ligand {2,6-bis[(S)-4-isopropyl-1-phenyl-4,5-dihydro-1H-2-imidazolyl]pyridine} (2.6mmol ) and 20 milliliters of 1,4-dioxane were added in a 100-milliliter single-necked flask, and the nitrogen flow was kept constant after replacing the air inside with nitrogen, cooled by an ice bath after magnetic stirring for 2 hours, and then added 2.7 grams of benzaldehyde (25 mmol) , 15 grams of nitromethane (250mmol) and N-methylmorpholine (0.27 milliliters, 2.5mmol), the reaction solution was stirred in ice-bath cooling for 24 hours, after thin plate chromatography detected no raw material benzaldehyde spots, then distillation under reduced pressure Remove volatile solvent, remove catalyst by silica gel filtration, filtrate is concentrated to obtain product 4.3 grams, yield 97%, HPLC measures e.e value to be 97%, nuclear magnetic spec...
Embodiment 2
[0036] 2 of the preparation method of embodiment 2 (R)-2-nitro-1-phenylethanol
[0037] In a 100 ml single-necked flask, add 0.5 g of 1-[2-(4S)-4-R-4,5-dihydro-2-oxazoline-ethyl]piperidine, 0.09 g of trifluoromethanesulfonate For copper (CuOTf), replace the air inside with nitrogen and keep the nitrogen flow constant. After 3 hours of magnetic stirring, cool in an ice bath, add 2.7 g of benzaldehyde (2 mol) and 15 g of nitromethane (6 mol) to anhydrous di A mixture was formed in methyl sulfoxide, and then the reaction solution was stirred in an ice bath for 12 hours. After thin-plate chromatography detected no raw material benzaldehyde spots, the volatile solvent was removed by distillation under reduced pressure, the catalyst was removed by silica gel filtration, and the filtrate was concentrated to obtain The product was 4.2 grams, the yield was 92%, and the e.e value determined by HPLC was 97%.
Embodiment 3
[0038] Example 3 Preparation of (1R, 2R)-2-nitro-1-phenyl-1,3-propanediol 1
[0039] Add 20 ml of 1,4-dioxane into a 100 ml single-necked flask, replace the air inside with nitrogen and keep the nitrogen flow constant, stir magnetically and add 0.75 g of paraformaldehyde (25 mmol), 4.2 g of (R)-2 -Nitro-1-phenylethanol (25mmol) and N-methylmorpholine (0.27 ml, 2.5mmol), the reaction solution was stirred in an ice bath for 24 hours, no raw material (R)-2- was detected by thin plate chromatography After the spots of nitro-1-phenylethanol, the volatile solvent was then distilled off under reduced pressure, purified by silica gel filtration, and the filtrate was concentrated to obtain 4.2 g of the product, with a yield of 85%. 1 H NMR (acetone-d 6 )δ: 3.46(ddd, J=3.2, 7.9, 12.0Hz, 1H), 3.70(s, 1H), 3.90(ddd, J=6.5, 9.2, 12.0Hz, 1H), 4.19~4.23(m, 2H) , 4.84 (ddd, J=3.2, 9.2, 9.2Hz, 1H), 5.08 (d, J=9.2Hz, 1H), 5.03~5.11(m, 1H), 7.31~7.48(m, 5H). 13 C NMR (acetone-d 6 )δ: 61.2, 7...
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