AlCl3‑Catalyzed Intramolecular Cyclization of N‑Arylpropynamides with N‑Sulfanylsuccinimides: Divergent Synthesis of 3‑Sulfenyl Quinolin-2-ones and Azaspiro[4,5]trienones

Switchable ortho/ipso-cyclization of N-arylpropynamides induced with N-sulfanylsuccinimides as general sulfur reagents is reported. In the presence of MeOH, para-fluoro N-arylpropynamides exclusively undergo the ipso-cyclization to give 3-sulfenyl azaspiro­[4,5]­trienones. Two kinds of bioactive heterocycles, benzothieno-[3,2-b]­quinoline and -[2,3-c]­quinolone, have been directly and efficiently prepared from the corresponding sulfenylated products.