Acetic acid, 2-(triphenylphosphoranylidene)-, ethyl ester → (R,E)-ethyl 5-(tert-butoxycarbonylamino)hex-2-enoate

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Reaction Steps

To a solution of (R)-tert-butyl 4-oxobutan-2-ylcarbamate (1.54 g, 8.22 mmol) in THF (25 mL) at rt was added (carbethoxymethylene)triphenylphosphorane (6.30 g, 18.1 mmol) in portions. The resulting clear solution was stirred at rt under argon for 3 days. The reaction mixture was concentrated and the oily residue was purified using silica gel chromatography (ISCO system) eluting with a gradient of 0-60% EtOAc/Hex to give (R,E)-ethyl 5-(tert-butoxycarbonylamino)hex-2-enoate (1.70 g, 6.61 mmol, 80% yield) as a colorless oil. 1H NMR (400 MHz, CDCl3) δ ppm 6.91 (dt, J=15.3, 7.5 Hz, 1H), 5.92-5.82 (m, 1H), 4.37 (s, 1H), 4.19 (q, J=7.1 Hz, 2H), 3.83 (s, 1H), 2.37 (t, J=6.6 Hz, 2H), 1.44 (s, 9H), 1.29 (t, J=7.1 Hz, 3H), 1.15 (d, J=6.7 Hz, 3H).

Provenance & Evidence