Journal of Organic Chemistry 2007-02-02

Synthesis of pyrazolo[1,5-alpha]pyrimidinone regioisomers.

Lori K Gavrin, Arthur Lee, Brian A Provencher, Walter W Massefski, Stephen D Huhn, Gregory M Ciszewski, Derek C Cole, John C McKew

Index: J. Org. Chem. 72(3) , 1043-6, (2007)

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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.