Dieckmann condensation explained

The Dieckmann condensation is the intramolecular chemical reaction of diesters with base to give β-keto esters.^[1] It is named after the German chemist Walter Dieckmann (1869–1925).^{[2] [3]} The equivalent intermolecular reaction is the Claisen condensation. Dieckmann condensations are highly effective routes to 5-, 6-, and 7-member rings, but poor for larger rings.

Reaction mechanism

Deprotonation of an ester at the α-position generates an enolate ion which then undergoes a 5-exo-trig nucleophilic attack to give a cyclic enol. Protonation with a Brønsted-Lowry acid (H₃O⁺ for example) re-forms the β-keto ester.^[4]

Due to the steric stability of five- and six-membered rings, these structures will preferentially be formed. 1,6 diesters will form five-membered cyclic β-keto esters, while 1,7 diesters will form six-membered β-keto esters.^[5]

Further reading

• Dieckmann, W. Ber. 1894, 27, 102 & 965
• Dieckmann, W. Ber. 1900, 33, 595 & 2670
• Dieckmann, W. Ann. 1901, 317, 51 & 93

See also

• Claisen condensation
• Gabriel–Colman rearrangement
• Thorpe reaction

Notes and References

1. Davis, B. R.; Garrett, P. J. Compr. Org. Synth. 1991, 2, 806-829. (Review)
2. Book: 10.1002/9780470771099.ch8. Rearrangement and cyclization reactions of carboxylic acids and esters. PATAI'S Chemistry of Functional Groups: Carboxylic Acids and Esters (1969). 341–373. 1969. Kwart. Harold. King. Kenneth. 9780470771099. S. Patai.
3. Schaefer, J. P. . Bloomfield, J. J. . The Dieckmann Condensation (Including the Thorpe-Ziegler Condensation) . Organic Reactions . 1967 . 15 . 1–203 . 10.1002/0471264180.or015.01 . 0471264180 .
4. Book: Janice Gorzynski Smith . Organic Chemistry . limited . 2nd . 2007 . 932–933 . 978-0073327495.
5. Web site: Organic Chemistry Portal . Dieckmann Condensation .