Reaction #53722

Reaction equation

3-iodo-5-nitro-1H-indazole

2-(trimethylsilyl)ethoxymethyl chloride

potassium hydroxide

→

3-iodo-5-nitro-1-(2-trimethylsilanylethoxymethyl)-1H-indazole

Solvents

water

dichloromethane

diisopropyl ether

water

Conditions

Workup

1. 1
   workup.ADDITIONare added over 15 minutes
2. 2
   Otheris reheated to a temperature in the region of 20° C
3. 3
   Extractionthe aqueous phase is extracted with 2 times 70 ml of dichloromethane
4. 4
   Washwashed with 2 times 70 ml of water
5. 5
   Dryingdried over magnesium sulfate
6. 6
   Filtrationfiltered
7. 7
   Concentrationconcentrated to dryness under reduced pressure (2 kPa) at a temperature in the region of 25° C
8. 8
   OtherThe residue thus obtained
9. 9
   Filtrationfiltered under hot conditions through paper
10. 10
    Otherrecrystallized
11. 11
    FiltrationThe crystals are filtered through sintered glass
12. 12
    Washwashed with 2 times 10 ml of diisopropyl ether
13. 13
    Otherdried under reduced pressure (2 kPa) at a temperature in the region of 20° C

Procedure

3-Iodo-5-nitro-1-(2-trimethylsilanylethoxymethyl)-1H-indazole can be obtained in the following way: 30 g of potassium hydroxide pellets are added to 30 ml of water at a temperature in the region of 0° C. After complete dissolution, 7 g of 3-iodo-5-nitro-1H-indazole, 50 ml of dichloromethane and then 82 mg of tetrabutylammonium bromide are added. The reaction mixture is stirred at a temperature in the region of 0° C. and 5 ml of 2-(trimethylsilyl)ethoxymethyl chloride are added over 15 minutes. The reaction mixture is stirred at a temperature in the region of 0° C. for 1.5 hours, and then 150 ml of water are added and the mixture is reheated to a temperature in the region of 20° C. After settling out, the aqueous phase is extracted with 2 times 70 ml of dichloromethane. The organic extracts are pooled, washed with 2 times 70 ml of water, dried over magnesium sulfate, filtered and then concentrated to dryness under reduced pressure (2 kPa) at a temperature in the region of 25° C. The residue thus obtained is dissolved in 40 ml of hot diisopropyl ether, filtered under hot conditions through paper and then recrystallized. The crystals are filtered through sintered glass, washed with 2 times 10 ml of diisopropyl ether and then dried under reduced pressure (2 kPa) at a temperature in the region of 20° C. 4.6 g of 3-iodo-5-nitro-1-(2-trimethylsilanylethoxymethyl)-1H-indazole are thus obtained in the form of a yellow solid (Rf=0.4, silica gel thin layer chromatography, eluent: cyclohexane/ethyl acetate (80/20 by volume)).

Source