Chelated amino acid ester enolates undergo clean 1,4-addition towards allenyl ketones 9, giving rise to unsaturated δ-keto amino acid esters 12 at low temperature. If the reaction is allowed to warm to room temperature, the enolate intermediates A undergo cyclization towards the corresponding α-pyrones 13.
螯合
氨基酸酯的烯醇盐对烯丙基酮9进行干净的1,4-加成,产生不饱和δ-酮
氨基酸酯12,反应在低温下进行。如果反应被允许升温至室温,烯醇盐中间体A将发生环化,生成相应的
α-吡喃酮13。