Reaction #7929

Reaction equation

4-bromo-9a-butyl-7-hydroxy-1,2,9,9a-tetrahydro-fluoren-3-one

nBuLi

hexane

→

4-bromo-9a-butyl-3-methylene-2,3,9,9a-tetrahydro-1H-fluoren-7-ol

Solvents

tetrahydrofuran

tetrahydrofuran

Conditions

Workup

1. 1
   Temperaturewas cooled in an ice bath
2. 2
   workup.ADDITIONwas added by syringe
3. 3
   Otherthe ice bath was removed
4. 4
   workup.STIRRINGThe resulting mixture was stirred at room temperature for 3.2 hours
5. 5
   workup.WAITat 50° C. for 1.5 hour
6. 6
   workup.WAITfinally at room temperature for an additional 17 hours
7. 7
   OtherThe mixture was partitioned between saturated aqueous NH4Cl (5 mL) and EtOAc (9 mL)
8. 8
   Washwashed with brine (4 mL)
9. 9
   Dryingdried over MgSO4
10. 10
    Filtrationfiltered
11. 11
    Otherevaporated under vacuum to an oil (90. mg)
12. 12
    OtherThe crude product was purified by preparative layer chromatography on a 0.1×20×20 cm silica gel GF plate
13. 13
    WashThe UV visible band at Rf 0.50-0.63 was eluted with EtOAc
14. 14
    ConcentrationThe eluant was concentrated under vacuum to a residue which

Procedure

A suspension of methyltriphenylphosphonium bromide (373 mg, 1.04 mmol) in anhydrous tetrahydrofuran (2 mL) was cooled in an ice bath and stirred under a nitrogen atmosphere while 2.5 N nBuLi in hexane (0.36 mL, 0.90 mmol) was added by syringe. The mixture was stirred at 0° C. for 10 minutes to complete formation of the methylenetriphenylphosporane reagent. A solution of 4-bromo-9a-butyl-7-hydroxy-1,2,9,9a-tetrahydro-fluoren-3-one (50 mg, 0.15 mmol) in tetrahydrofuran (1 mL) was added to the reaction mixture and the ice bath was removed. The resulting mixture was stirred at room temperature for 3.2 hours, then at 50° C. for 1.5 hour, and finally at room temperature for an additional 17 hours. The mixture was partitioned between saturated aqueous NH4Cl (5 mL) and EtOAc (9 mL). The organic phase was acidified with 2N HCl (0.2 mL), washed with brine (4 mL), dried over MgSO4, filtered, and evaporated under vacuum to an oil (90. mg). The crude product was purified by preparative layer chromatography on a 0.1×20×20 cm silica gel GF plate using 3:1 hexanes-EtOAc as developing solvent. The UV visible band at Rf 0.50-0.63 was eluted with EtOAc. The eluant was concentrated under vacuum to a residue which was lyophilized from benzene to afford 4-bromo-9a-butyl-3-methylene-2,3,9,9a-tetrahydro-1H-fluoren-7-ol.

Source