Cascade Annulation for Synthesizing Chromenopyrrolones from <i>o</i>-Hydroxyphenyl Enaminones and 2-Halo-<i>N</i>-alkyloxyacetamides

A cascade cyclization reaction comprising two halogenation reactions and a Michael addition was developed for the synthesis of chromeno[2,3-<i>c</i>]pyrrole-3-ones <b>4</b>. Additionally, another cascade cyclization reaction, which involves a halogenation reaction followed by two intramolecular Michael additions, was established for the synthesis of chromeno[2,3-<i>b</i>]pyrrole-2-ones <b>5</b>. Both types of compounds were synthesized from <i>o</i>-hydroxyphenyl enaminones and 2-halo-<i>N</i>-alkyloxyacetamides through a process that facilitated the intramolecular formation of C-C, C-O, and C-N bonds to effectively establish two fused rings in a single operation. This novel protocol is efficient, uses readily accessible starting materials, and operates under mild conditions, demonstrating tolerance for various functional groups while achieving good yields.