Pinner condensation

What is Pinner condensation?

The Pinner condensation, also known as the Pinner synthesis, involves a strong base-promoted condensation between a non-N-substituted amidine and a β-keto ester or β-diketone, resulting in the formation of a pyrimidine. This reaction was first reported by Pinner (University of Berlin) in 1884.

Pinner condensation - general reaction scheme - Pinner synthesis
Pinner condensation

While the Pinner condensation offers a promising method for synthesizing pyrimidine, the successful reduction of the carbonyl group at the 6-position and dehydration is necessary for the preparation of pyrimidine hydrocarbon. Zinc reduction in either NaOH or HCl solution is commonly used, although it can be challenging to achieve in some cases.

Pinner condensation - general reaction scheme - Pinner synthesis
Pinner condensation

However, an excess amount of sodium ethylate at high temperature has been found to result in a higher yield of pyrimidine. Interestingly, extending the reaction time does not seem to have a significant impact on the yield.

References

Pinner, A. (1884), Ueber die Einwirkung von Acetessigäther auf die Amidine. [On the effect of acetoacetic ether on amidines] Ber. Dtsch. Chem. Ges., 17: 2519-2520. https://doi.org/10.1002/cber.188401702173

Shares