Divergent cyclisations of 2-(5-amino-4-carbamoyl-1H-pyrazol-3-yl) acetic acids with formyl and acetyl electrophiles

Smyth, Lynette A., Matthews, Thomas P., Horton, Peter N., Hursthouse, Michael B. and Collins, Ian (2007) Divergent cyclisations of 2-(5-amino-4-carbamoyl-1H-pyrazol-3-yl) acetic acids with formyl and acetyl electrophiles. Tetrahedron, 63 (39), 9627-9634. (doi:10.1016/j.tet.2007.07.034).

Abstract

The reaction of 2-(5-amino-4-carbamoyl-1-methyl-1H-pyrazol-3-yl)acetic acid and triethylorthoformate did not give the expected dihydropyrazolo[4,3-c]pyridin-4-one product as described in literature, but formed an alternative cyclic imide product, fully characterised by NMR and X-ray crystallography. This mode of reaction was shown to be general to other 1-substituted-2-(5-amino-4-carbamoyl-1H-pyrazol-3-yl)acetic acids. The outcome of the cyclisation was highly sensitive both to the nature of the reagents used and also to the acidity of the reaction medium, such that a number of interesting bicyclic heterocycles could be produced in a controlled fashion from the single starting material. The major tautomeric forms of the bicyclic products in solution were found to vary according to their substitution pattern.

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Contributors

Author: Peter N. Horton

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