Reactions of dianions of acyclic β-enamino ketones with electrophiles. Part 5. Esters: synthesis of pyridin-4-one and pyran-4-one derivatives
Abstract
The electrophilic attack of esters to dianions of β-monosubstituted amino-α,β-unsaturated ketones and the subsequent cyclisation of the addition product offers a valuable generalisation of the synthesis of N-substituted pyridin-4-ones and pyran-4-ones. The reaction proceeds in good to high yields with α′-dianions. A side metallation reaction is observed with aliphatic esters. Product distribution is influenced by the nucleophilic ability of nitrogen and the electrophilicity of the carbonyl group which are involved in cyclisation. The reaction of γ-dianions with esters is the first example of a reactivity of these systems which resembles alkyl organometallic reagents more than enolates. In fact the major product of this reaction is the alcohol with incorporation of two enaminone moieties.
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