Clauson-Kaas reaction

What is Clauson-Kaas reaction?

The Clauson-Kaas and Tyle discovery in 1952 marked the first reporting of a reaction now known as the Clauson-Kaas procedure. This procedure involves the synthesis of pyrrole derivatives through the condensation of a primary aliphatic or aromatic amine with 2,5-dimethoxy-tetrahydrofuran in the presence of an acid catalyst.

Clauson-Kaas reaction - Clauson-Kaas procedure
Clauson-Kaas reaction

Acid catalysts such as acetic acid, phosphorus pentoxide, and 4-chloropyridinium hydrochloride are commonly used in this reaction. While the Clauson-Kaas reaction has been successful in converting primary amino groups into pyrrole groups, it may not be effective in synthesizing pyrroles that contain acidic labile groups, such as imidazole groups. In such cases, an alternative method of preparation involves using a primary amine and 1,4-dichloro-1,4-dimethoxybutane in the presence of an acid catalyst such as Amberlyst A-21.

References

Clauson-Kaas, N. and Tyle, Z., “Preparation of Cis- and Trans 2,5-Dimethoxy-2-(acetamidomethyl)-2,5-dihydrofuran, of Cis- and Trans 2,5-Dimethoxy-2-(acetamidomethyl)-tetrahydrofuran and of 1-Phenyl-2-(acetamidomethyl)-pyrrole.Acta Chemica Scandinavica, 1952, 6, 667-670
DOI: 10.3891/acta.chem.scand.06-0667

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