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

                  Prepared a suspension of 27.006 g of D-mannitol (I) and 42.012 g of ZnCl₂ in 210 mL of acetone.  Stirred at rt  for 3 h.  TLC (Et₂O, PMA) showed product spot at Rf 0.51.  The reaction mixture was then filtered through Celite to remove the insoluble material and the filtrate was poured into a biphasic mixture of 210 mL of Et₂O and a solution of 53.0 g of K₂CO₃ in water.  A heavy precipitate formed.  The mixture was stirred for 30 min and filtered through a pad of silica gel.  The solvent was removed by rotary evaporation to afford a white solid.  The product was isolated by flash chromatography on silica gel using Et₂O.  The product was a white solid.

 

mp 116-117 C.

 

¹H NMR (CDCl₃, 300 MHz) d 4.17 (m, H2, H5), 4.10 (m, H1, H6), 3.95 (m, H1, H6), 3.73 (m, H3, H4), 2.56 (d, J = 6.8 Hz, OH), 1.40 (s, CH₃), 1.34 (s, CH₃).

 

notes

 

The product of this reaction, D-mannitol diacetonide, is a useful precursor for the formation of D-glyceraldehyde acetonide by cleavage with Pb(OAc)₄ (see Horton, D.; Thomson, J.B.  J. Org. Chem.  1968, 33, 728).  Cleavage of the diol can also be accomplished using NaIO₄ (see Oxidative Cleavage, this chapter).