(S)-4-Isopropyl-3-(1-naphthylmethyl)-2,5,5-triphenyl-1,3,2-oxazaborolidine (ca. 6% in Toluene, ca. 0.1mol/L)

Typical procedure: To a dried Schlenk flask was charged CH₂Cl₂ (1.95 mL) and a 0.1 M solution of (S)-4-isopropyl-3-(1-naphthylmethyl)-2,5,5-triphenyl- 1,3,2-oxazaborolidine in CH₂Cl₂ (300 micro-L, 0.03 mmol) under argon atmosphere. After this solution cooled to -78 °C, a 0.1 M solution of 1-[bis(trifluoromethanesulfonyl)methyl]-2,3,4,5,6-pentafluorobenzene in CH₂Cl₂ (250 micro-L, 0.025 mmol) was added dropwise. The solution was stirred for 15 minutes at the same temperature. To this catalyst solution was added ethyl acrylate (108 micro-L, 1.0 mmol) dropwise. After 1-2 minutes, mono-substituted cyclopentadiene (1.25 mmol) (1:1 (v/v) room temperature solution in CH₂Cl₂) was added dropwise. Upon completion, the reaction was quenched with 100 micro-L of Et₃N at the same temperature. The reaction mixture was allowed to warm to room temperature and the solvent was removed in vacuo. The crude product was purified by flash column chromatography (elution with hexanes/ether = 30:1) to give (1R, 2R, 4R)-5-Methyl-bicyclo[2.2.1]hept- 5-ene-2-carboxylic acid ethyl ester (173 mg, 96% yield, 99 %ee).