Preparation of Some Bis(fluorodimethylsilyl)alkanes

It has been established that the demethylation of bis(trimethylsilyl)alkanes of the general formula Me3SiRSiMe3 by concentrated sulfuric acid, followed by fluorination with ammonium hydrogenfluoride, can successfully be used for the method generally applicable to the preparation of bis(fluorodimethylsilyl)- alkanes, FMe2SiRSiMe2F. Although Si-Me cleavage was the main reaction in most cases, some part of the reaction gave a cleavage between silicon and the R grouping.The ease of the cleavage of R from silicon was found to decrease in the following order: CH2,CHMe>(CH2)2>(CH2)3>(CH2)4,(CH2)5,(CH2)6>CHCl>CMe2