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Updated: Jan 2, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Synthesis of pyrazolo[1,5-alpha]pyrimidinone regioisomers
Lori K Gavrin1, Arthur Lee, Brian A Provencher
1Department of Exploratory Medicinal Chemistry and Chemical Technologies, Wyeth Research, 200 CambridgePark Drive, Cambridge, Massachusetts 02140, USA. gavrinl@wyeth.com
Abstract:
This work describes two distinct routes to prepare pyrazolo[1,5-alpha]pyrimidin-7-ones and two distinct routes to prepare pyrazolo[1,5-alpha]pyrimidin-5-ones. Use of 1,3-dimethyluracil as the electrophile in the preparation of the pyrimidin-5-one regioisomer represents a correction of previously reported results. Also, a novel reaction to prepare this isomer was identified and the reaction mechanism elucidated. This work provides the experimentalist with complimentary synthetic pathways that afford either the pyrimidin-7-one or the pyrimidin-5-one regioisomer.
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