88% |
With N-Bromosuccinimide; sodium hydrogencarbonate; triphenylphosphine In dichloromethane at 0 - 20℃; for 1h; |
14
Triphenylphosphine (22.9 g, 87.3 mmol) was added to a stirred solution of methyl-15-hydroxypentadecanoate (19.0 g, 69.8 mmol) in dichloromethane (350 mL)and then sodium bicarbonate (0.5 g) was added. The mixture was cooled to 10 °C and NBS (16.16 g, 90.8 mmol) was added portion wise over 20 min at 0 °C.Stirring was continued at r.t. for 1 hour, when TLC indicated that the reactionwas complete. A saturated solution of sodium bisulfate (120 mL) was added andthe organic layer was separated. The aqueous layer was re-extracted with CH2Cl2 (2 x 100 mL) and the combined organic layers were washed with water (100 mL),dried, and evaporated. The residue was treated with petrol/ethyl acetate (20:1,250 mL) and refluxed for 30 min then the triphenylphosphonium oxide wasfiltered off and washed with petrol/ethyl acetate (20:1, 150 mL). The filtrate was evaporated and the crude product was purified by column chromatography eluting with petrol/ethyl acetate (20:1) to give a white solid of the title compound 25 (20.6 g, 88 %), |
88% |
With N-Bromosuccinimide; sodium hydrogencarbonate; triphenylphosphine In dichloromethane at 0 - 20℃; |
Methyl 15-bromopentadecanoate
Triphenyl phosphine (24.3 g, 92.6 mmol) was added to a stirred solution of methyl 15-hydroxypentadecanoate (20.0 g, 72.3 mmol) in CH2Cl2 (350 mL) and then sodium bicarbonate (0. 5 g) was added. The mixture was cooled to 0oC and NBS (17.0 g, 95.5 mmol) was added portion wise at 0oC. Stirring was continued at r.t for 1 h, when TLC showed that the reaction was complete. A saturated solution of sodium bisulphate (150 mL) was added and the mixture was extracted with dichloromethane (200 mL). The aqueous layer was re-extracted with CH2Cl2 (2 × 100 mL) and the combined organic layers were washed with water (50 mL). The solution was dried, the solvent was evaporated and petrol/ethyl acetate (20:1, 100 mL) were added. The mixture was refluxed for 30 min; the triphenylphosphonium oxide was filtered through a pad of celite and washed with petrol/ethyl acetate (20:1, 100 mL). The solvent was evaporated and the crude product was purified by column chromatography eluting with petrol/ethyl acetate (10:1) to give the title compoundas a white solid (22 g, 88%); δH(400 MHz, CDCl3): 3.67 (3H, s), 3.41 (2H, t, J 6.9 Hz), 2.31 (2H, t, J 7.6 Hz), 1.9 - 1.82 (2H, quintet, J 7 Hz), 1.64 - 1.60 (2H, m), 1.44 - 1.39 (2H, m), 1.30 - 1.26 (18H, m); δC(101 MHz, CDCl3): 174.3, 63.1, 51.4, 34.1, 34.0, 32.9, 29.6, 29.5, 29.4, 29.3, 29.2, 28.8, 28.2, 25.0; νmax/cm-1: 2919, 2851, 1739, 1463. |