Acetic acid, 2-(triphenylphosphoranylidene)-, ethyl ester → (R)-ethyl 3-(N-benzyloxycarbonylpyrrolidin-2-yl)-2-propenoate

Participants

Reaction Steps

To a stirred solution of N-carbobenzyloxypyrrolidine-2-carboxaldehyde (1.17 g, 5.00 mmol) in anhydrous tetrahydrofuran at -78° C. was added (carboethoxymethylene)-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 to afford the title compound as a clear, colorless oil (1.11 g, 3.65 mmol, 73%): 1H NMR (CDCl3) δ 7.34-7.25 (m, 5H), 6.89-6.76 (m, 1H), 5.88-5.74 (m, 1H), 5.18-5.05 (m, 2H), 4.60-4.43 (m, 1H), 4.17 (q, J=7.1 Hz, 2H), 3.55-3.40 (m, 2H), 2.11-2.00 (m, 1H), 1.90-1.75 (m, 3H), 1.28 (t, J=7.1 Hz, 3H); 13C NMR (CDCl3) [Note: due to slow nitrogen inversion two conformers of the products are seen by NMR spectroscopy] δ 166.3, 154.7, 147.9, 147.4, 136.6, 128.4, 127.9, 120.9, 66.9, 65.8, 60.4, 58.1, 57.7, 46.8, 46.4, 31,6, 30.8, 23.5, 22.8, 22.6, 15.3, 14.2.

Provenance & Evidence