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As has been discussed previously – acetoacetic ester synthesis and malonic ester synthesis are non-selective, in that, they can produce dialkylated products. This particular property of these reactions can be made use of to synthesize cyclic compounds using a alkyl dihalide. This reaction can be used to even produced highly strained 4-membered rings as is shown below.

Steps:

1. In presence of base and alkyl dihalide, the beta-keto ester or malonic ester can react to produce the substituted compound. (note – increasing the alkyl chain length would yield bigger cyclic structures, and R1 can be either alkyl or ester)
2. Since base is still present and one of the halides is still present on the product itself, the disubstitution leads to formation of a ring. (note- chances of another alkyl dihalide from reacting with this product is lesser compared to the alkyl halide which is already attached to it).
3. Once the cyclic compound is formed the reaction need not stop there – the product can undergo hydrolysis under the basic conditions to yield the acid (at this stage if R1 is also an ester it may undergo hydrolysis).
4. Finally acidification with slight heating may promote the compound to lose 1 molecule of carbon dioxide to yield the product.

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References

1. Advanced Organic Chemistry: Reactions and synthesis. By Francis A. Carey, Richard J. Sundberg
2. Organic-Chemistry.org (accessed on February 06, 2011)