Dieckmann Cyclization Comparative Reaction

The Dieckmann Cyclization is one of the important reactions that we have evaluated. Not only is this reaction of a higher order of importance as a carbon-carbon bond-forming reaction, but it is one of the best ways to form 5-membered carbocyclic rings. This reaction involves the base-catalyzed cyclization of dicarboxylic esters to give ß-ketoesters, the intramolecular equivalent of the Claisen condensation. We have investigated the yields obtained using DMSO with dimsyl ion as the base versus a traditional method employing toluene and sodium metal. The graph below displays one of the examples where the usage of DMSO provides significantly higher yields:

dieckmann cyclization comparative reaction: % yield vs. solvent tested

Yield in the Dieckmann Cyclization

(of diethyl adipate to 2-carbethoxycyclopentanone)

dieckmann cyclization comparative reaction: % yield vs. time

Kinetic measurements show that reaction rates and yields are consistently higher in DMSO. The high selectivity indicates that side reactions leading to polymer formation are insignificant in this solvent.

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