an enol. Upon treatment of this cyclic 1,3-ketoester with aqueous HCl, an acyl-lactone rearrangement takes place. The structure of the resulting pyran was confirmed by an X-ray analysis. The ability of the rearrangement product to lose its carboxylic group under unexpected mild conditions was used for the synthesis of the corresponding 3-unsubstituted cyclic hemi-ketal.
δ-戊内酯与
三氟乙酸乙酯的克莱森缩合产生α-三
氟乙酰基-
δ-戊内酯,其以烯醇形式完全存在于CDCl 3溶液中。用HCl
水溶液处理该环状1,3-
酮酯后,发生酰基-内酯重排。通过X射线分析确认了得到的
吡喃的结构。重排产物在意外的温和条件下失去其羧基的能力被用于合成相应的3-未取代的环状半
缩酮。