1) Olefination of 3-phenyl-6-bromoindene

SyntheticPage 697
Published Oct 04, 2013


Reaction Scheme

Procedure

Procedure A: The synthesis was performed using standard Schlenk techniques under a nitrogen atmosphere. To a sealed scintillation vial charged with indene 1 (43.7 mg, 0.161 mmol), anhydrous 2-MeTHF (1.6 mL) was added. The solution was cooled to 0 oC and n-BuLi (0.070 mL, 0.161 mmol, 2.5 M solution in hexanes) was added dropwise. The reaction mixture was then stirred for 1 h. p-tolualdehyde (0.020 mL, 0.169 mmol) was added to the reaction mixture at 0 oC. The reaction mixture was returned to RT and stirred for 20 h. TLC was used to monitor the reaction.* The reaction mixture was quenched and washed with saturated ammonium chloride (3 x 1 mL) and extracted with diethyl ether (3 x 1 mL). The organic layer was dried over magnesium sulfate, filtered into a roundbottom flask, and further eluted with diethyl ether (3 mL). The solvent was evaporated under reduced pressure. The crude product was dissolved in dichloromethane and purified using a preparatory plate (90:10, hexanes:toluene), yielding a light red solid, benzofulvene 2 (28.7 mg, 47%).

Procedure B: The synthesis was performed using standard Schlenk techniques under a nitrogen atmosphere. To a sealed scintillation vial charged with indene 1 (100 mg, 0.369 mmol), anhydrous heptane (3.7 mL) was added. The solution was cooled to 0 oC and n-BuLi (0.15 mL, 0.369 mmol, 2.5 M solution in hexanes) was added dropwise. The reaction mixture was warmed to RT and stirred overnight.  A tan precipitate develops.  The heptanes was removed under reduced pressure and anhydrous 2-MeTHF (3.7 mL) was added.  The solution was cooled to 0 oC and p-tolualdehyde (0.048 mL, 0.406 mmol) was added dropwise. The reaction mixture was returned to RT and stirred for 20 h. TLC was used to monitor the reaction.* The reaction mixture was quenched and washed with saturated ammonium chloride (3 x 2 mL) and extracted with diethyl ether (3 x 2 mL). The organic layer was dried over magnesium sulfate, filtered into a roundbottom flask, and further eluted with diethyl ether (3 mL). The solvent was evaporated under reduced pressure. The crude product was dissolved in dichloromethane and purified using a preparatory plate (90:10, hexanes:toluene), yielding a light red solid, benzofulvene 2 (81.0 mg, 59%).

*An aliquot was removed from the crude reaction mixture and diluted for TLC.

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2) Olefination of 3-phenyl indene

SyntheticPage 698
Published Oct 22, 2013


Reaction Scheme

Procedure

The synthesis was conducted under a nitrogen atmosphere using standard Schlenk techniques. To a 15 mL scintillation vial was added: 3-phenylindene (0.150 g, 7.80 x 10-4 mol), heptane (8.0 mL, 0.1 M) and a stir bar. The reaction was stirred at 0 °C for approximately 10 minutes.  Dropwise1, n-Butyllithium (0.330 mL, 8.19 x 10-4 mol) was added and the flask was allowed to return to room temperature and stirred overnight (~20 hours).

Heptane was removed under reduced pressure.  To the remaining precipitate was added: 2-methyltetrahydrofuran (8.0 mL, 0.1 M) and the reaction was cooled to 0 °C and stirred2 for approximately 10 minutes at which point p-Tolualdehyde (0.100 mL, 8.58 x 10-4 mol) was added dropwise and the reaction was stirred overnight at room temperature (≈ 20 h).

The reaction was quenched with 3 mL of aqueous NH4Cl.  The sample was washed with brine solution (3 x 5 mL) and extracted with diethyl ether (3 x 5 mL)3.  The organic layer was dried over MgSO4 and then gravity filtered.  The solvent was removed under reduced pressure and the crude product was purified via preparatory plate (90:10 Hexane:Toluene) yielding a highly colored yellow/orange solid (130 mg, 57% yield).

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