NMR-Data from Canadian Journal of Chemistry, 77, 146 (1999)


This compound has been synthesized and the analytical data have been published in the above mentioned article. The tert.-butyldimethylsilyl group is a frequently occuring protecting group in organic chemistry. A CAS-search using SCIFINDER revealed 207,820 structures, when using this structural fragment as query.

A prediction of the carbon chemical shiftvalues for this protecting group leads to values of -5ppm for the Si-CH3 group, 18ppm for the quarternary carbon and 25ppm for the -CH3 in the tBu-group. (Values rounded, nearly identical values obtained by HOSE and NN calculation using CSEARCH)

When looking into the above mentioned article (Compound #8) we find the following values for the protecting group: 53.27 (SiC(CH3)3), 25.89 (SiC(CH3)3), 18.22 (Si(CH3)2)


Carbon position
53.27 ppm
25.89 ppm
18.22 ppm

Obviously there is some misassignment when looking at the signals at 18.22ppm and 25.89ppm respectively. The open question is the remaining signal at 53.27ppm. The only explanation I can offer is - when reading the experimental part carefully - dichloromethane, which was used during the last step of workup.

Within the article there is no numbering scheme for the compounds given - in such a case the naumbering from the nomenclature is usually applied. In this particular case the C-2 (138.29ppm) and C-1 (124.56ppm) [the two aromatic signals which are clearly assigned] should also be reversed - maybe the term 'C-ipso' is with respect to the bromine substitution. At least the data representation is not very 'user-friendly' in the case of the aromatic carbons, whereas the signals of the prtecting group are definitely wrong.

Page written by:   Wolfgang.Robien(at)univie.ac.at
Page online since:  March 4th, 2008