Reaction #554632

Reaction equation

CH3COONa

1

tigogenin

CH3COCH3

CH3COOH

→

2

Yield 69.5%

3β-Acetoxy-5α-pregn-16-en-20-one

Yield 69.5%

Solvents

isopropanol

water

(CH3CO)2O

water

(CH3CO)2O

Conditions

Workup

1. 1
   workup.WAITboiled an additional 2 h
2. 2
   Temperaturecooled to 40° C.
3. 3
   workup.STIRRINGstirred 20 min
4. 4
   Temperaturecooled to room temperature
5. 5
   workup.STIRRINGstirred an additional hour
6. 6
   Temperaturegradually heated
7. 7
   workup.DISTILLATIONto distill off acetone
8. 8
   Othera temperature of 115-117° C.
9. 9
   workup.WAITboiled for 1.5 h
10. 10
    Temperaturecooled to room temperature
11. 11
    workup.ADDITIONtreated with water (425 mL)
12. 12
    FiltrationThe resulting precipitate was filtered off
13. 13
    Washwashed with water
14. 14
    Otherrecrystallized from methanol:acetone (3:1)

Procedure

A mixture of 1 (50 g, 120.0 mmol), (CH3CO)2O (150 mL), and C5H5N (10 mL) was boiled for 1 h, cooled to 100° C., stirred, treated with TiCl4 (2.5 g, 13.16 mmol) in (CH3CO)2O (2.5 mL), boiled an additional 2 h, cooled to 40° C., treated gradually with CH3COONa (10 g) dissolved in water (25 mL), stirred 20 min, cooled to room temperature, poured into CH3COCH3 (220 mL) and CH3COOH (220 mL), oxidized by addition of CrO3 (15 g) in water (7.5 mL) at 15-18° C., stirred an additional hour, treated with isopropanol (7.5 mL), gradually heated to distill off acetone and reach a temperature of 115-117° C., boiled for 1.5 h, cooled to room temperature, and treated with water (425 mL). The resulting precipitate was filtered off, washed with water, and recrystallized from methanol:acetone (3:1) to afford 2 (29 g, 69.5%), mp 158-162° C., lit. mp 158-162° C. [2].

Source