wt/vol

 

wt/vol

MW

moles

density

equivs.

yield

I

1.583 g

500.97

0.0032

 

1.0

 

II

0.210 g

251.31

0.0008

 

0.25

 

III

30 mL

-

-

 

 

 

IV

1.100 g

386.71

0.0028

 

 

(90%)

 

Procedure:  100 mL 1-neck flask, stirbar, septum, N2 inlet

                  Dissolved 1.583 g of diene I in 30 mL of absolute EtOH.  Stirred at rt.  Added 0.210 g of PPTS.  After 16 h, the reaction mixture was quenched with sat. aq. NaHCO3 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 20:80 EtOAc-hexanes as eluant.  The product was a clear, colorless oil. 

notes

 

The use of PPTS for the selective deprotection of silyl ethers was first reported for the selective removal of TBS protected alcohols in the presence of DPS protected alcohols (see Prakash, C.; Saleh, S.; Blair, I.A.  Tetrahedron Lett.  1989, 30, 19).  Here, the reagent is used to selectively cleave a primary TBS ether in the presence of a secondary.