反应详情

温度

65 °C

A solution of carbon tetrabromide (18.12 g, 54.63 mmol) in pyridine (100 mL) was added to a solution of monotosylate (50) (14.9 g, 49.66 mmol) and triphenylphosphine (26.1 g, 99.32 mmol) in pyridine (150 mL) over 30 minutes, then the mixture heated at 65° C. for 1.5 hours under an atmosphere of argon. Water (200 mL) was added then the aqueous phase extracted with dichloromethane (5×100 mL). The organic phase was washed with brine (50 mL), then dried (MgSO4), filtered and reduced in vacuo to leave a residue which was azeotroped with toluene (5×50 mL). Flash chromatography over silica, eluting with diethyl ether:heptane mixtures 0:100 to 100:0 gave bromotosylate (46) (7.70 g, 43%) as a white solid. [□]D17+68.6° (c=0.51, CHCl3).

1. extractionthe aqueous phase extracted with dichloromethane (5×100 mL)
2. washThe organic phase was washed with brine (50 mL)
3. dry with materialdried (MgSO4)
4. filtrationfiltered
5. customto leave a residue which
6. customwas azeotroped with toluene (5×50 mL)
7. washFlash chromatography over silica, eluting with diethyl ether