Molecular Iodine Enabled Cascade Oxidation and Annulation for the Construction of Polycyclic 5‐aroyl‐5,6‐dihydropyrazolo[1,5‐ <i>c</i> ]Quinazolines

ABSTRACT A practical, metal‐free, molecular iodine‐mediated one‐pot protocol has been developed for the construction of 5‐aroyl‐5,6‐dihydropyrazolo[1,5‐ c ]quinazolines from readily accessible aryl/heteroaryl acetophenones and 5‐(2‐aminophenyl)‐1 H ‐pyrazoles, thereby forming two new C‐N bonds. Notably, this represents the first report on the synthesis of 5‐aroyl‐substituted pyrazolo[1,5‐ c ]quinazolines, whereas all previously reported methods are limited to 5‐aryl analogues. The methodology exhibits broad substrate scope and functional group tolerance, extending beyond acetophenones to include phenylacetylenes, styrene, and 2‐hydroxyacetophenone, delivering the desired heterocycles in moderate to good yields. Further, benzyl alcohols serve as viable precursors under identical conditions to afford 5‐aryl‐5,6‐dihydropyrazolo[1,5‐ c ]quinazolines. The synthetic utility of the protocol is demonstrated by gram‐scale synthesis. The structure of a representative product 3a was unambiguously determined by single‐crystal XRD. Mechanistic investigations, supported by HRMS studies, provide insight into the plausible reaction pathway.