我们合成手性的胺可以通过Ellman试剂首先合成亚磺酰胺在酸性条件下脱出亚磺酰胺就可以得到手性胺。如果我们底物含有对酸敏感的基团的时候,酸性脱出亚磺酰胺就会有意想不到的副产物产生。最近有篇文献报道在碱性条件下脱出亚磺酰胺就可以避免有酸性基团的影响。
In summary, we have developed an iodine mediated single electron transfer process for the deprotection of tertbutanesulfinyl and p-toluenesulfinyl units. For most substrates used in this research, the yields are good to excellent using only catalytic amounts of iodine. Our new methods are especially useful for the deprotection of N-tert-butanesulfinyl amines with acid sensitive structure motifs and should find more applications in the synthesis of complex natural products.
Method A: (For acid sensitive substrates) To a solution of sulfinyl amines (0.5 mmol) in THF/H2O (1:1, 10 mL) was added Na2CO3(1.5 mmol, 3.0 eq.) and DMAP (0.1 mmol, 0.2 eq.). The reaction mixture was stirred for 5 min at 20 °C before addition of I2 (1.25 mmol, 2.5 eq.) under an argon atmosphere. The resulting mixture was then stirred at 20 °C under argon for 16-24 h. After consumption of starting materials, the reaction was quenched by water (5 mL) and aqueous sodium thiosulphate (2N, 0.1 mL) at room temperature. The mixture was extracted with CH2Cl2(3 × 5 mL), and the combined organic phases were dried (Na2SO4), and concentrated.The residue was chromatographed on basic aluminium oxide (petroleum ether 60-90 °C : ethyl acetate : Et3N= 3 : 1 : 0.02 or ethyl acetate : Et3N= 1 : 0.01) to afford the product.
Method B: (Other substrates less labile to acids)To a solution of sulfinyl amines (0.5 mmol) in THF/H2O (5:1, 10 mL) was added iodine (0.1 mmol, 0.2 eq.). The reaction mixture was then stirred at 50 °C under air or under nitrogen until completely consumption of sulfinyl amines. The reaction mixture was cooled to room temperature and diluted with water (15-20 mL). After removal of THF under reduced pressure, an aqueous solution of sodium thiosulphate (0.2 N, 0.2 mL) was added. The resulting mixture was then washed with Et2O (3 × 5 mL), and the aqueous phase was treated with saturated aqueous solution of NaHCO3 (5 ml). The resulting aqueous mixture was then extracted with CH2Cl2(3 × 5 mL) and the combined organic phases were washed with brine and dried over Na2SO4. After filtration, the solvent was removed under reduced pressure to afford the amines. Chromatography on basic aluminium oxide might be required for some amines.
Ref:Chem. Commun., 2014,50, 6259-6262
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