Rothemund reaction

What is Rothemund reaction?

The Rothemund reaction is a widely used method for synthesizing porphyrins. The reaction was first reported by Rothemund in 1935 and involves the one-pot thermal condensation of aldehydes with pyrroles to yield porphine or isoporphine. This reaction is also known as the Rothemund synthesis or Rothemund condensation and is sometimes referred to as the Rothemund-Lindsey reaction.

Rothemund reaction - general reaction scheme - Rothemund-Lindsey reaction - Rothemund synthesis
Rothemund reaction

R = H, alkyl, aryl

The reaction conditions for this condensation can vary, with different yields achieved under different conditions. Higher yields of porphyrins can be obtained with the addition of heterocyclic bases such as 2,4,6-collidine or metal ion species such as Cu(I) and Co(II). The use of an electron-deficient aldehyde typically results in a higher yield of porphyrin than the use of an electron-rich aldehyde, and the substituent on the aldehyde controls the reaction course. However, the formation of other porphyrin analogues, such as chlorin, sapphyrin, isosmaragdyrin, ozaphyrin, hexaphyrin, and corrole, complicates the reaction and makes it difficult to isolate pure porphyrin. Among these analogues, there may be inverted or N-confused porphyrins, in which the positions of nitrogen and carbon atoms are interchanged in one of the pyrrole rings.

References

Rothemund, P. (1935). Formation of porphyrins from pyrrole and aldehydes. Journal of the American Chemical Society, 57(10), 2010-2011. DOI: 10.1021/ja01313a510

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