Lithium hexamethyldisilazide, reaction with ketones

The products of the reaction of ketones with lithium hexamethyldisilazide have been studied by Collum and co-workers by an extensive use of the Li and NMR spectroscopy Vun couplings have been found to be particularly useful. 

This reaction can sometimes be useful in synthesis. In the Honda et al. formal synthesis of securinine,2h N-benzylamino-ketone (97) was treated with lithium hexamethyldisilazide and then sorbic anhydride. This gave dienyl ester 98 by O-alkylation of the initially formed enolate anion. When the nitrogen protecting group was... 

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