5-(methoxymethyl)cyclopenta-1,3-diene

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Add molecular sieves (3 Å, 12.0 g), (S)-(−)-α-methylbenzylamine (6.4 mL, 50.0 mmol) to a solution of ethylglyoxalate (10.3 mL, 50.0 mmol) in dichloromethane (200 mL) cooled in an ice bath. Stir the mixture at 0° C. for 2 h, and then cool to −78° C. Add trifluoroacetic acid (4.10 mL, 55.0 mmol), boron trifluoride etherate (6.90 mL, 55.0 mmol), and 5-methoxymethyl-1,3-cyclopentadiene (60.0 mmol, prepared in situ by adding cyclopentadienylsodium (2.0 M in THF, 30.0 mL, 60.0 mmol) to a solution of chloromethyl methyl ether (5.70 mL, 75.0 mmol) in tetrahydrofuran (30 mL) at −55° C.) with a 5 min interval between each addition. Stir for 2 h at −78° C. and refrigerate (−20° C.) overnight. Quench the reaction with saturated aqueous sodium bicarbonate solution (200 mL) and stir the mixture vigorously for 15 min. Separate the layers, dry the organic layer (magnesium sulfate), concentrate, and purify (silica gel chromatography 10:90 to 30:70 ethyl acetate:hexanes) to give the title compound (3.95 g, 25%). cooled in an ice bath cool to −78° C between each addition Stir for 2 h at −78° C. refrigerate (−20° C.) overnight Quench the reaction with saturated aqueous sodium bicarbonate solution (200 mL) stir the mixture vigorously for 15 min Separate the layers dry the organic layer (magnesium sulfate) concentrate purify (silica gel chromatography 10:90 to 30:70 ethyl acetate:hexanes)