Dieckmann condensation

4 real reactions from the literature, on esters. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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1. Dieckmann: diethyl 3,3-dibutylhexanedioate (an ester) with 1) NaH; 2) HCl gives 3,3-dibutylcyclopentanone (the cyclic β-keto ester). 85% yield.

   DieckmannJ. Org. Chem. 1994, 59, 5496

2. Dieckmann: an ester with 1) LiHMDS; 2) HCl workup gives the cyclic β-keto ester. 89% yield.

   DieckmannEur. J. Org. Chem. 2000, 2605

3. Dieckmann: an ester with 1) NaOEt, EtOH, 3 h / reflux; 2) cool to 0 C, add MeI gives the cyclic β-keto ester. 68% yield.

   DieckmannJ. Chem. Soc. 1960, 2842

4. Dieckmann: dimethyl 4-propan-2-ylideneheptanedioate (an ester) with NaH, DME gives methyl 2-oxo-5-(propan-2-ylidene)cyclohexanecarboxylate (the cyclic β-keto ester).

   DieckmannChem. Commun. 1967, 753