wt/vol

 

wt/vol

MW

moles

density

equivs.

yield

I

0.389 g

154.24

0.0025

 

1.0

 

II

0.477 g

156.61

0.0030

 

1.2

 

III

0.180 g

24.00

0.0075

 

3.0

 

IV

5 mL

-

-

 

 

 

V

0.550 g

274.39

0.0020

 

 

(79%)

 

Procedure:  50 mL 1-neck flask, stirbar, septum, N2 inlet

                  Dissolved 0.389 g of alcohol I in 2.5 mL of dry DMF.  Stirred;  cooled to 0 C.  Added 0.180 g of powdered NaH.  Stirred for 30 min.  Some gas evolution noted.  Let warm to rt and stirred for 30 min.  Cooled back to 0 C and added a solution of 0.477 g of PMBCl (II) in 2.5 mL of DMF dropwise over a 15 min period.  Let stir overnight as bath warmed to rt.  After 16 h, TLC (10:90 EtOAc-hexanes, PMA) showed product spot at Rf 0.58.  Poured reaction mixture into water and extracted with EtOAc.  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 5:95 Et2O-hexanes as eluant.

 

notes

 

This reaction is a simple SN2 substitution with in situ formed alkoxide displacing chlorine.