Ninhydrin reaction with phenylethylamine: unavoidable by-products


Ninhydrin and phenylethylamine reacted to form a complex mixture from which four products were isolated: a benzo-fused spiroheterocyclic and a pyrrole product resulting from tricomponent condensation between ninhydrin, phenylethylamine and phenylacetaldehyde produced in situ, a 2-amino-1,3-indandione dimerisation-dehydrogenation product and a Schiff base. This article analyses these compounds’ structure and proposes reaction mechanisms contributing to knowledge regarding ninhydrin and phenylethylamine chemical reactivity.

Graphic abstract

Ninhydrin and phenylethylamine reacted to form a benzo-fused spiroheterocyclic, a pyrrole, a 2-amino-1,3-indandione dimerisation-dehydrogenation product and a Schiff base.

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We would like to thank the Universidad Nacional de Colombia (DIB Research Project No. 37398) for providing financial support. On behalf of all authors, the corresponding author states that there is no conflict of interest.

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Correspondence to Rodolfo Quevedo.

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Gonzalez-Oñate, A., Quevedo, R. Ninhydrin reaction with phenylethylamine: unavoidable by-products. J Chem Sci 132, 49 (2020).

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  • Ninhydrin
  • phenylethylamine
  • phenylacetaldehyde
  • Schiff base