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A Parallel Approach to 7‑(Hetero)arylpyrazolo[1,5‑a]pyrimidin-5-ones

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posted on 04.04.2018, 00:00 by Daniel C. Schmitt, Nootaree Niljianskul, Neal W. Sach, John I. Trujillo
A modular, two-pot assembly of 7-arylpyrazolo­[1,5-a]­pyrimidones from aryl/heteroaryl halides and aminopyrazoles in library format was developed. Sonogashira coupling of aryl bromides with triethyl orthopropiolate, followed by in situ orthoester hydrolysis, provides access to β-aryl ynoates, which undergo regioselective cyclocondensation with aminopyrazoles. The ability to vary the C7 vector of 7-arylpyrazolo­[1,5-a]­pyrimidones in two steps using readily available (hetero)­aryl halides significantly enhances synthetic access to this challenging vector.