How is Diethyl 1,1-cyclobutanedicarboxylate (CAS: 3779-29-1) typically synthesized?

Diethyl 1,1-cyclobutanedicarboxylate (CAS: 3779-29-1) is typically synthesized from 1,1-cyclobutanedicarboxylic acid and diethylamine. The reaction involves the substitution of the carboxylic acid groups with ethyl esters. This process often uses a mild base like triethylamine as a catalyst. The reaction is highly selective and yields up to 95% of the desired product. The yield can be improved by optimizing reaction conditions such as temperature and concentration.