Retro- -Brook organolithiums

Brook rearrangements may be carried out with either catalytic or stoichiometric base. With catalytic base, the reaction can be considered an equilibrium between 41 and 42. The strength of the Si-0 bond (about 500-520 kJ mol-1) compared with the Si-C bond (about 310-350 kJ mol-1) means that, provided the anion 33 forms reasonably rapidly (some degree of stabilisation is required), Brook rearrangement (alkoxide formation) is favoured over retro-Brook. Organolithiums 33 may be present as intermediates in the catalytic Brook rearrangement, but their reactivity cannot be exploited under these conditions. 

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