[Br:1][CH2:2][CH2:3][CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH2:9][CH2:10][CH2:11][C:12]([OH:14])=[O:13].[Cl-].[Ca+2].[Cl-].[CH3:18]O>>[Br:1][CH2:2][CH2:3][CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH2:9][CH2:10][CH2:11][C:12]([O:14][CH3:18])=[O:13]11-Bromoundecanoic acid (commercial material, 25.0 g, 94 mmol), Duolite H+ resin (10 g), calcium chloride (26.2 g, 94 mmol) and methanol (700 ml) were stirred for 15 h. The methanol was removed and dichloromethane was added. The mixture was washed with water, dried (Na2SO4) and concentrated. Distillation gave pure 103 (22.0 g, 84%) with b.p. 103°-104° (2×10-2 torr). 1H-NMR (CDCl3, Me4Si) δ 3.67 (s, 3H, MeO), 3.41 (t, 2H, J=6.8 Hz, Br--CH2), 2.31 (t, 2H, J=7.3 Hz, CH2CO).
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