The investigation of a transsilylation reaction for the preparation of silyl esters: Reactivity correlated with 29Si NMR resonance frequencies

Article abstract of DOI:10.1016/S0022-328X(97)00146-0

The investigation of a transesterification reaction involving silicon exchange (transsilylation) between a silyl ester and a chlorosilane is reported. The reaction studied involves an equilibrium interchange between trimethylsilyl benzoate and several chlorosilanes, as a preparation of various silyl esters and trimethylsilyl chloride as a volatile by-product. An interesting reactivity balance was observed, in which the reaction with some of the chlorosilanes required an initiating catalyst to proceed. A correlation between the ²⁹Si NMR chemical shifts of the chlorosilanes and their respective reactivities was observed. Chlorosilanes having ²⁹Si NMR chemical shifts greater than 31 ppm (referenced to tetramethylsilane standard at 0 ppm) required the use of a nucleophilic catalyst to initiate the reaction. Reaction of trimethylsilyl benzoate occurred without an initiator with chlorosilanes having ²⁹Si NMR chemical shifts of 5 to 19 ppm; for those resonating between 19 and 31 ppm, an initiator accelerated the reaction and gave improved yields of transsilylated product. N,N-Dimethylformamide and sodium iodide were found to be effective and convenient catalysts/initiators for the reaction.