Leveraging in situ N-tosylhydrazones as diazo surrogates for efficient access to pyrazolo-[1,5-c]quinazolinone derivatives.

We developed a transition metal-free methodology for the construction of pyrazoloquinazolinone derivatives. The strategy involves a one-pot reaction wherein the N-tosylhydrazone and its corresponding diazo derivative are generated in situ, followed by an intramolecular 1,3-dipolar cycloaddition-ring expansion to provide the pyrazolo-[1,5-c]quinazolinone motif. This approach enables straightforward access to a diverse range of highly functionalized N-heterocyclic compounds in good yields (up to 92%).