Siloxane-containing derivatives of benzoic acid: chemical transformation of the carboxyl group

This study presents a route for chemical transformation of Si-derivatives of benzoic acid - p-carboxyphenyldisiloxane and bis(p-carboxyphenyl)disiloxane - to a wide range of corresponding esters, thioesters, amides, etc. The reactions proceed under mild reaction conditions, in the presence of carbonyldiimidazole as a carboxyl group activator, making it possible to obtain the desired products in gram scale with high selectivity (without destruction of the organosiloxane backbone) and yields up to 97%. The structure of the resulting compounds was confirmed by IR, HRMS ESI, 1D and 2D H-1/C-13/Si-29 NMR spectroscopy, and X-ray diffraction data. It is shown by the example of some Si-derivatives of amides, that they form HOF-like structures in the crystalline state.