Selectivity, cation partition reaction

For other substrates, formation of a more stable cationic species drives the [1,2] shift reaction, although thermodynamic partitioning of cationic intermediates and/or subsequent rearrangements can lead to complex product mixtures10. For systems where equilibration of an initially formed cation would be expected to yield mixtures, such as methyl 5-hydroxy-7-trimethylsilyl-bicyclo[2.2.2]octane-2-carboxylates, selective bond migration has been effected by the introduction of a silyl substituent, which serves the dual role of stabilization of the fi carbocation and subsequent elimination to yield an olefinic product14. 

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