Iodine‐Mediated Three‐Component Tandem Reaction for Synthesizing Indolo‐Fused 3‐Sulfenylpyrazolo[1,5‐a]pyrimidines

A method for synthesizing indolo‐fused 3‐sulfenylpyrazolo[1,5‐a]pyrimidines has been developed through a one‐pot, iodine‐mediated domino reaction using indole‐3‐carbaldehydes, 3‐aminopyrazoles and dichalcogenides or thiophenols. Mechanistic studies suggest that the reaction proceeds through a radical pathway during the C‐S bond formation, with an iodonium ion intermediate driving the cyclization step. Additionally, some products exhibit significant antitumor activity.