Reaktion #159448

Reaktionsgleichung

trimethyl borate

3-(2-ethyl-5-iodophenyl)bicyclo[3.2.1]octane-2,4-dione

iso-propyl magnesium chloride lithium chloride

→

3-(2,4-dioxo-bicyclo[3.2.1]oct-3-yl)-4-ethylphenylboronic acid

Ausbeute 90.8%

Lösungsmittel

dichloromethane

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONis added dropwise
2. 2
   Temperaturto maintain a temperature below −60° C
3. 3
   workup.STIRRINGis further stirred for 5 minutes
4. 4
   workup.WAITadditionally at room temperature for 1 hour
5. 5
   SonstigeThe solution is quenched with 2M hydrochloric acid
6. 6
   Extraktionextracted with ethyl acetate (×3)
7. 7
   Trocknendried over magnesium sulfate
8. 8
   Filtrationfiltered
9. 9
   Einengenthe filtrate concentrated in vacuo
10. 10
    Sonstigeto give an orange-coloured gum
11. 11
    Sonstigethen precipitated with iso-hexane

Vorschrift

To a solution of 3-(2-ethyl-5-iodophenyl)bicyclo[3.2.1]octane-2,4-dione (0.65 g, 1.77 mmol) in anhydrous tetrahydrofuran (15 ml) at −10° C. is added iso-propyl magnesium chloride lithium chloride complex (10.6 ml, 10.6 mmol, 1M in tetrahydrofuran) dropwise over 10 minutes. The reaction mixture is stirred at this temperature for 1.5 hours, then cooled to −78° C., at which point trimethyl borate (1.39 ml, 12.4 mmol) is added dropwise to maintain a temperature below −60° C. After re-cooling to −78° C. the mixture is further stirred for 5 minutes, then additionally at room temperature for 1 hour. The solution is quenched with 2M hydrochloric acid and extracted with ethyl acetate (×3). All organic fractions are combined, dried over magnesium sulfate, filtered and the filtrate concentrated in vacuo to give an orange-coloured gum. This crude product is dissolved in a minimum amount of dichloromethane then precipitated with iso-hexane to afford 3-(2,4-dioxo-bicyclo[3.2.1]oct-3-yl)-4-ethylphenylboronic acid (0.46 g, 90%) as a cream-coloured solid.

Quelle