反应详情

2-Mercapto-4-nitrophenol (2.0 g) and 2,4-dichlorobenzaldehyde (2.0 g) were heated under reflux for 6 hours in toluene (70 ml) containing a catalytic amount (0.2 g) of p-toluenesulphonic acid monohydrate. Water formed in the reaction was separated by means of a Dean-Stark apparatus. The resulting reaction mixture was evaporated under reduced pressure, and the residue extracted with cyclohexane. The cyclohexane solution was then evaporated and the residue chromatographed on silica gel using methylene chloride/5% (v/v) methanol as eluant. The material obtained at this stage was contaminated with unreacted aldehyde. This was removed by stirring a methylene chloride solution of the crude product with 30% aqueous sodium bisulphite for 2 hours and then washing the solution successively with saturated sodium bicarbonate solution and water. After drying over anhydrous sodium sulphate, the methylene chloride was removed under reduced pressure. Crystallisation of the residue afforded the pure product as pale yellow crystals (0.7 g, 21%), mp 106°-108° C.

1. customwas separated by means of a Dean-Stark apparatus
2. customThe resulting reaction mixture
3. customwas evaporated under reduced pressure
4. extractionthe residue extracted with cyclohexane
5. customThe cyclohexane solution was then evaporated
6. customthe residue chromatographed on silica gel
7. customThe material obtained at this stage
8. customThis was removed
9. washwashing the solution successively with saturated sodium bicarbonate solution and water
10. dry with materialAfter drying over anhydrous sodium sulphate
11. customthe methylene chloride was removed under reduced pressure
12. customCrystallisation of the residue