反应详情

A solution of 24 (3.90 g, 0.030 mol), mercaptoacetic acid (3.32 g, 0.036 mol) and p-TsOH.H2O (0.28 g, 1.5 mmol) in acetonitrile (600 ml) was heated at reflux for 3.5 hours. During the period of reflux, four portions of 25 ml each were drained from a Dean-Stark trap (to remove the water-acetonitrile azeotrope). Analysis of the reaction solution by TLC (6:1 hexane:AcOEt) revealed one major new component and no unreacted aldehyde (visualized by PMA and 2,4-DNP stains). The reaction solution was allowed to stir at room temperature for 16 hours, and then evaporated to dryness. The residue was partitioned between concentrated NaHCO3 (50 ml) and AcOEt (75 ml); the aqueous portion was extracted with additional AcOEt (2×75 ml). The organic fractions were combined, dried (MgSO4), filtered, and concentrated in vacuo. The crude material (6 g) was purified by flash chromatography (125 grams silica gel with 20% ethyl acetate in hexane). Compound 25 (3.27 g, 16 mmol, 53%) was obtained as an oil: TLC (3:1 hexane:AcOEt)—one spot with Rf=0.41; 1H-nmr (CDCl3)—compatible with structure; mass spectrum (FAB)—m/z=205.1 (M+1).

1. temperatureat reflux for 3.5 hours
2. temperatureDuring the period of reflux
3. customto remove the water-acetonitrile azeotrope)
4. customevaporated to dryness
5. customThe residue was partitioned between concentrated NaHCO3 (50 ml) and AcOEt (75 ml)
6. extractionthe aqueous portion was extracted with additional AcOEt (2×75 ml)
7. dry with materialdried (MgSO4)
8. filtrationfiltered
9. concentrationconcentrated in vacuo
10. customThe crude material (6 g) was purified by flash chromatography (125 grams silica gel with 20% ethyl acetate in hexane)