Procedure:  500 mL 1-neck flask, stirbar, septum, N₂ inlet

                  Dissolved 4.452 g of diol I in 200 mL of dry THF.  Stirred; cooled to 0 C.  Added 11.0 mL of n-BuLi (2.5 M in hexanes).  Obtained a white precipitate.  After 35 min, 3.27 mL of BnBr was added.  After 4 h, TLC analysis showed only unreacted I at Rf 0.37 (EtOAc, CAM).  Added 1.003 g of Bu₄NI.  After 69 h at rt, TLC again showed only unreacted I.  The reaction mixture was then refluxed for 48 h.  TLC analysis showed product spot at Rf 0.84 (EtOAc, CAM).  The reaction was quenched with sat. aq. NH₄Cl and extracted with Et₂O.  The organic layer was dried over MgSO₄, filtered and the solvent was removed by rotary evaporation.  The product was isolated by flash chromatography on silica gel using Et₂O as eluant.  The product was a clear, pale yellow oil. 

 

notes

 

Here, n-BuLi is used to deprotonate one of the hydroxyl groups to afford the alkoxide which is insoluble in THF and precipitates.  This allows for the protection of a single hydroxyl group of the diol.  The stoichiometry and order of addition should be considered important; even though the alkoxide precipitates it is still probably a good idea not to have excess base around in the presence of either the diol or the alkoxide.