To a stirred solution of N-carbobenzyloxypyrrolidine-2-carboxaldehyde or N-carbobenzyloxypiperidine-2-carboxaldehyde (5.00 mmol) [S. Kiyooka, et al., J. Org. Chem., 5409 (1989) and Y. Hamada, et al., Chem. Pharm. Bull., 1921 (1982)] in anhydrous tetrahydrofuran at -78° C. was added (carbethoxymethylene) triphenylphosphorane (2.09 g, 6.00 mmol. 1.2 eq) as a solid portionwise. The resulting reaction mixture was stirred at room temperature under nitrogen for 2 hours, and then heated at reflux under nitrogen for 1 hour. The reaction mixture was evaporated under reduced pressure and the residue was column chromatographed using silica gel (approximately 100 g) and elution with 20% diethyl ether in hexanes afforded either ethyl 3-(N-benzyloxycarbonylpyrrolidin-2-yl)-2-propenoate or ethyl 3-(N-benzyloxycarbonylpiperid-2-yl)-2-propenoate.
