Cascade Annulation\nfor Synthesizing Chromenopyrrolones\nfrom <i>o</i>‑Hydroxyphenyl Enaminones and 2‑Halo‑<i>N</i>‑alkyloxyacetamides

A cascade cyclization reaction comprising two halogenation\nreactions\nand a Michael addition was developed for the synthesis of chromeno[2,3-<i>c</i>]pyrrole-3-ones <b>4</b>. Additionally, another cascade\ncyclization reaction, which involves a halogenation reaction followed\nby two intramolecular Michael additions, was established for the synthesis\nof chromeno[2,3-<i>b</i>]pyrrole-2-ones <b>5</b>.\nBoth types of compounds were synthesized from <i>o</i>-hydroxyphenyl\nenaminones and 2-halo-<i>N</i>-alkyloxyacetamides through\na process that facilitated the intramolecular formation of C–C,\nC–O, and C–N bonds to effectively establish two fused\nrings in a single operation. This novel protocol is efficient, uses\nreadily accessible starting materials, and operates under mild conditions,\ndemonstrating tolerance for various functional groups while achieving\ngood yields.