定义Definition
迪克曼缩合是二元羧酸二酯在强碱作用下发生分子内克莱森缩合，生成环状 β-酮酸酯的反应，最适合形成五元和六元环。
The Dieckmann condensation is the intramolecular Claisen condensation of a diester under strong base, giving a cyclic β-keto ester; it works best for five- and six-membered rings.
机理Mechanism
与克莱森缩合相同：一个酯基 α 位形成烯醇负离子，进攻分子内另一个酯羰基，消除烷氧负离子成环；产物 β-酮酸酯被碱去质子化驱动反应。己二酸二乙酯得 2-氧代环戊烷甲酸乙酯，庚二酸二乙酯得六元环产物。
As in the Claisen: an enolate attacks the other ester within the same molecule and expels alkoxide; deprotonation of the cyclic β-keto ester drives the reaction. Diethyl adipate gives ethyl 2-oxocyclopentanecarboxylate; diethyl pimelate gives the six-membered analogue.
由来Origin
德国化学家瓦尔特·迪克曼于 1894 年报道。
Reported by the German chemist Walter Dieckmann in 1894.
应用Applications
环状 β-酮酸酯经烷基化、水解脱羧可得取代环酮，是合成环戊酮、环己酮衍生物的常用方法。大环需高稀释条件，常改用其他方法。
Alkylation, hydrolysis and decarboxylation of the cyclic β-keto ester give substituted cyclic ketones. Larger rings need high dilution and are usually made otherwise.
反应Reactions
NaOEt/EtOH 或 NaH/甲苯，加热；酸化后处理
NaOEt/EtOH or NaH/toluene with heating; acidic work-up
形成酯烯醇负离子。
Enolate formation.
分子内进攻另一酯羰基成环。
Intramolecular attack on the other ester closes the ring.
消除乙氧负离子，产物去质子化，酸化。
Loss of ethoxide, deprotonation and acidification.
五元环 β-酮酸酯。
A five-membered β-keto ester.
年表Timeline
- 1894
迪克曼报道该反应
Dieckmann reports the reaction