Studies in silanol synthesis: internal nucleophiles and steric hindrance

As a model system for the synthesis of complex silanediols, N,N-dimethyl 3-(tert-butyldiphenylsilyl)propionamide was prepared and treated with triflic acid, resulting in the removal of one phenyl group and yielding a silanol. Even with a large excess of triflic acid, only a single phenyl group could be removed. This contrasts with a diphenylsilyl group flanked by a pair of amides, for which both phenyl groups are rapidly cleaved. A combination of steric hindrance by the tert-butyl group and lack of a second internal nucleophile appears to limit triflic acid-mediated phenyl hydrolysis from the silicon.