The investigation of a transsilylation reaction for the preparation of silyl esters: reactivity correlated with Si-29 NMR resonance frequencies
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abstract
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. 1997 Elsevier Science S.A.
