Two types of enolates can be formed stepwise from enolisable 1,3-dicarbonyl-substituted propene systems in the presence of catalytic amounts of 1,4-diazabicyclo[2.2.2]octane (DABCO) to accomplish a highly selective carbocyclization with β,γ-unsaturated α-keto esters, giving functionalized spiroketones with vicinal quaternary stereocenters.
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