Reaktion #3160

Reaktionsgleichung

water

triisopropylborate

b-bromo-2-octylcoumaran

butyllithium

→

2-octylcoumaran-5-boronic acid

Ausbeute 67.1%

Lösungsmittel

THF

hexane

THF

hexane

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigenitrogen atmosphere on a dry ice-acetone bath at an inner temperature of -70° to -68° C., followed
2. 2
   workup.STIRRINGby stirring for 50 minutes at the same temperature
3. 3
   workup.STIRRINGby stirring for minutes at the same temperature
4. 4
   SonstigeThereafter, the cooling bath was removed
5. 5
   workup.ADDITIONfollowed by gradual addition of 9.5 ml of 10%-hydrochloric acid
6. 6
   SonstigeAfter the reaction
7. 7
   Extraktionsubjected to extraction with isopropyl ether
8. 8
   Waschenby washing with water
9. 9
   Trocknendrying with mirabilite and distilling-off of the solvent
10. 10
    Sonstigeto obtain a residue
11. 11
    workup.WAITthe mixture was left
12. 12
    Sonstigeto precipitate a crystal
13. 13
    FiltrationThe crystal was recovered by filtration

Vorschrift

Then, 2.00 g (6.43 mM) of b-bromo-2-octylcoumaran and 28 ml of dry THF were placed in a 100 ml-three-necked flask. To the mixture, 4.5 ml (7.20 mM) of a 1.6M solution of butyllithium in hexane was added dropwise under stirring and nitrogen atmosphere on a dry ice-acetone bath at an inner temperature of -70° to -68° C., followed by stirring for 50 minutes at the same temperature. To the resultant mixture a solution of 3.2 ml (13.9 mM) of triisopropylborate in 5.7 ml of dry THF was added dropwise in 10 minutes at an inner temperature of -73° to -68° C., followed by stirring for minutes at the same temperature. Thereafter, the cooling bath was removed and the inner temperature was increased to room temperature, followed by gradual addition of 9.5 ml of 10%-hydrochloric acid. After the reaction, the reaction mixture was poured into water and subjected to extraction with isopropyl ether, followed by washing with water, drying with mirabilite and distilling-off of the solvent to obtain a residue. To the residue, hexane was added and the mixture was left standing in a freezer to precipitate a crystal. The crystal was recovered by filtration to obtain 1.19 g of 2-octylcoumaran-5-boronic acid (Yield: 67.1%).

Quelle