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

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.