Malonic ester synthesis retrosynthetic analysis

Cyclopropanecarboxylic acid may be prepared by a malonic ester synthesis, as retrosynthetic analysis shows. 

A convenient way to determine when to apply the acetoacetic ester or malonic ester approach to a synthetic problem is to incorporate the synthon concept into retrosynthetic analysis. A synthon is a structural unit in a molecule that is related to a synthetic operation. A CH2CO2H group is a synthon that alerts us to the possibility of preparing a target by a malonic ester synthesis. Likewise, a CH2C(0)CH3 group is a synthon that suggests an acetoacetic synthesis. 

For retrosynthetic analysis, a carboxylic acid with one or two aUgrl groups bonded to the a-carbon is a characteristic product of the acetoacetic ester synthesis starting with diethyl malonate. 

---