Natural Science Forum / Chemistry / Organic Synthesis / March 2006

Hi,
I did a TMSCl protection on a diol at a late stage in my synthesis (7
mg Start Mat. excess TMSCl, Py, DMAP, DCM/DMF = 10/1, r.t. over night)
and I obvously protected both hydroxy groups.
- one on a secundary alcohol which appeats at 0.1 ppm.
- a second TMS obviously on an alpha-hydroxy ketone (hydroxy is
tertiarty) at 0.5 ppm (in C6D6).
Could someone estimate the NMR shift for the TMS group in the latter
case?

           \
            C=O
           /
TMSO-C-O-CHR
          \
           CH2R

I expected it to be around 0 ppm as well. Has someone seen a TMSO- at
0.5 ppm?
Thank you for your help,

spic