Indene 1 (Prepared in House by method of SP696)

n-BuLi (2.5 M solution in hexanes, Acros Organics)

p-tolualdehyde (TCI)

2-MeTHF (≥99%, Anhydrous, Sigma-Aldrich)

Diethyl Ether (Sigma-Aldrich)

Dichloromethane (Sigma-Aldrich)

Saturated Ammonium Chloride

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.

¹H NMR (CDCl₃, 500 MHz): δ ppm 2.54 (s, 3H), 7.27 (s, 1H), 7.38-7.39 (m, 2H), 7.51-7.61 (m, 6H),  7.69 (d, J = 8.3 Hz, 2H), 7.77-7.79 (m, 2H), 8.00 (s, 1H)

¹³C NMR (CDCl₃, 125 MHz): δ ppm 21.66, 119.76, 121.27, 122.86, 123.67, 128.54, 128.54, 128.97, 129.88, 129.94, 129.98, 130.60, 134.15, 135.61, 137.57, 139.38, 139.57, 141.25, 146.72

GC-MS EI [M^.+]: Predicted: 372.05, Actual: 372; Predicted: 374.06, Actual: 374; Predicted: 373.05, Actual: 373

Lu, W.; Zhu, Q.; Yan, C. Synth. Commun., 1997, 27, 3985-3990.

Alcalde, E.; Mesquida, N.; Frigola, J.; López-Pérez, S.; Mercè, R. Org. Biomol. Chem., 2008, 6, 3795-3810