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Comins三氟甲磺酸化試劑

(2024-03-02 20:14:32) 下一個

N,N-二三氟甲磺酰基-5-氯-2-氨基吡啶或N,N-二三氟甲磺酰基苯胺,此類芳胺的二三氟甲磺酰胺被稱為Comins三氟甲磺酸化試劑。其可以將酮類,酯,硫代酸酯轉化為相應的三氟甲磺酸烯酯。由於此試劑的活性較高,反應條件溫和,因此廣泛應用於全合成。

【Comins DL, Tet Lett 1992, 33, 6299】

N-(2-Pyridyl)triflimide (1). A 2-L, two-necked, round-bottomed flask equipped with a mechanical stirrer (Note 1) and a rubber septum is charged with 2-aminopyridine (19.859 g, 0.211 mol) (Note 2) and pyridine (35.04 g, 35.88 mL, 0.443 mol) (Note 3) in 800 mL of dichloromethane (CH2Cl2) (Note 4) under an argon atmosphere. The reaction mixture is cooled to −78°C and a solution of triflic anhydride (125 g, 74.54 mL, 0.443 mol) (Note 5) in 150 mL of CH2Cl2 is added dropwise via a cannula over 3.5 hr with vigorous stirring. After the solution is stirred for 2 hr at −78°C, the cooling bath is removed and stirring is continued at room temperature for 19 hr. The reaction mixture is quenched with 50 mL of cold water and the layers are separated. The aqueous layer is extracted with CH2Cl2 (4 × 50 mL). The combined organic extracts are washed with cold aqueous 10% sodium hydroxide (1 × 150 mL), cold water (1 × 100 mL), brine (1 × 100 mL) and dried over magnesium sulfate. After filtration, the solvent is removed under vacuum to give 69 g of the crude product. After Kugelrohr distillation (Note 6), 61 g (81%) of pure N-(2-pyridyl)triflimide (bp 85–100°C/0.25 mm, mp 41–42°C) (Note 7) is obtained as a white solid.

【Joseph SP, Org Synth1997, 74, 77】

Enol triflate (5). Under N2 at 78 C, b-thio-butyrolactone 4 (0.17 mL, 2 mmol) in THF (5 mL) was treated with KHMDS (4.4 mL, solution of 0.5 M in PhMe). After 1 h stirring, 3 (780 mg, 2 mmol) in THF (2 mL) was added. After 3 h at 78 C, quenching (H2O), extraction (Et2O), evaporation and chromatography (Al2O3 neutral) gave 342 mg of 5 (73%).

【O’Neil IA, Synlett1995, 151】

To a solution of compound 13 (15 mg, 0.052 mmol) in dry THF (5 mL) was added KHMDS (115 μL, 0.057 mmol) at -78 o C, and the mixture was stirred at the same temperature for 30 min. To this solution was added Comins reagent (N-(5-chloro-2-pyridyl) triflimide) (23 mg, 0.057 mmol) in dry THF (2 mL) -78 o C, and the mixture was then stirred at the same temperature for additional 3 h. The reaction was quenched by addition of a saturated solution of NH4Cl (5 mL), and the mixture was extracted with Et2O (3 x 10 mL). The combined extracts were dried over sodium sulfate. The solvent was removed in vacuo and the residue was purified by a flash chromatography on silica gel (hexane/ethyl acetate,10/1) to give 13a (21 mg) in 92% yield as white solid. It is worthwhile to mention that excessive KHMDS will lead to lower yielding.

【Yang Z, J Am Chem Soc2010, 132, 13608】

Enol triflate (–)-67: To a solution of ketone (–)-65 (1.80 g, 5.48 mmol) in THF (100 mL) at –78 °C was added KHMDS (1.5 equiv, 0.5 M in PhMe, 16.4 mL, 8.22 mmol). The reaction mixture was stirred 10 min before a solution of Commins reagent (1.5 equiv, 3.22 g, 8.22 mmol) in THF(20 mL) was added dropwise. The resulting mixture was warmed to –40 °C then quenched with saturated aqueous NH4Cl solution (50 iphasic mixture was extracted with Et2O (50 mL TfO (MgSO4), and concentrated under reduced pressure. The crude residue was purified by flash column chromatography (silica, Et2O/hexanes, 1 → 4%) to furnish enol triflate (–)-67 (2.43 g, 5.15 mmol, 94%) as a colorless oil.

【Nicolaou KC, J Am Chem Soc2010, 132, 7138】

 

 

編譯自:Organic Syntheses Based On Name Reactions, 3RdEd, A. Hassner, Page 94.

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