Methanol → Methyl cis-7-bromo-5-heptenoate

Participants

Reaction Steps

To a solution of alcohol 39 (1.48 g, 9.36 mmol) and carbon tetrabromide (3.40 g, 10.25 mmol) in dry CH2Cl2 (50 mL) was added triphenylphosphine (2.70 g, 10.30 mmol) in portions. The reaction mixture was stirred for 40 min and MeOH (1 mL) was added. Concentration on a rotary evaporator, followed by flash chromatography using 50:1 hexane/EtOAc as eluent, gave 40 as a colorless oil (1.98 g, 96%): IR (neat) 3020 (w), 2945, 2860 (w), 1740 (s), 1435, 1370, 1200, 1165 cm-1 ; 1H NMR (CDCl3) δ 5.77 (m, J1 =10.5 Hz, J2 =8.3 Hz, J3 =1.4 Hz, 1H), 5.56 (m, J1 =10.6 Hz, J2 =7.5 Hz, 1H), 3.98 (d, J=8.1 Hz, 2H), 3.67 (s, 3H), 2.34 (t, J=7.4 Hz, 2H), 2.19 (dq, J1 =7.5 Hz, J2 =1.4 Hz, 2H), 1.74 (p. J=7.3 Hz, 2H); 13C NMR (CDCl3) δ 173.55, 134.48, 126.26, 51.37, 33.06, 26.60, 26.01, 24.28. A minor amount (ca. 5%) of methyl trans-7-bromo-5-heptenoate could be seen in the 1H NMR spectrum at δ 3.93.

Provenance & Evidence