Reaktion #4882

Reaktionsgleichung

dry ice

diisopropylamine

n-butyllithium

3,5-dichloropyridine

→

3,5-Dichloro-4-pyridinecarboxylic acid

Lösungsmittel

tetrahydrofuran

hexane

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturwhile maintaining the above temperature
2. 2
   workup.ADDITIONTwenty minutes subsequent to that addition
3. 3
   Sonstigeto evaporate overnight at room temperature
4. 4
   Waschenwashed with 3×30 ml of methylenechloride
5. 5
   Filtrationfiltered
6. 6
   Sonstigeto precipitate out the product
7. 7
   TemperaturAfter cooling
8. 8
   Sonstigethe precipitate was collected
9. 9
   Sonstigerecrystallized from ethyl acetate/hexane giving 1.9 g (29%) of white analytically pure crystals, m.p. 231°-35° C. (decomp.)

Vorschrift

To a solution of 4.96 ml (0.036 mole) of diisopropylamine in 200 ml of tetrahydrofuran at -65° C. under a nitrogen blanket was added dropwise 14.9 ml of 2.5M n-butyllithium in hexane while maintaining the above temperature. Twenty minutes subsequent to that addition, a solution 5.0 g (0.034 mole) of 3,5-dichloropyridine in 30 ml tetrahydrofuran at -60° to -70° C. was added. The reaction mixture was stirred at -70° C. for 1/2 hr, poured onto a large excess of dry ice and allowed to evaporate overnight at room temperature. The residue was taken up in 100 ml of dilute aqueous sodium hydroxide, washed with 3×30 ml of methylenechloride and filtered. The filtrate was acidified to ~pH 2 with dilute hydrochloric acid to precipitate out the product. After cooling, the precipitate was collected and recrystallized from ethyl acetate/hexane giving 1.9 g (29%) of white analytically pure crystals, m.p. 231°-35° C. (decomp.).

Quelle