Synthesis of 5,6-Dihydro­pyrazolo­[1,5‑<i>c</i>]quina­zolines through Gold-Catalyzed Chemoselective Bicyclization of <i>N</i>‑Propargylic Sulfonylhydrazones

An efficient method for the preparation of 5,6-dihydro­pyrazolo­[1,5-c]­quinazolines via gold­(I)-catalyzed chemoselective bicyclization of N-propargylic sulfonyl­hydrazones has been developed. This process relies on the chemoselective cyclization of the hydrazone nitrogen instead of the usually favored aniline nitrogen onto the alkyne. The synthetic utility of the current strategy is demonstrated through the synthesis of a potential Eg5/Kinesin spindle protein inhibitor.