As is clear from Scheme I the success of the reaction will depend on the ability of the second equivalent of organometallic to add to the rather hindered 8-keto silane formed in the initial step. 5 Thus, enolization or reduction are possible alternatives to addition to the carbonyl of the 8-keto silane. It would be expected, therefore, that increased steric demand on either the ester or the organometallic (R4M) would lead to lower yields of the olefins and higher ...