Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides
نویسندگان
چکیده
Two new fates of imine intermediates formed on radical cyclizations of ene-sulfonamides have been identified, reduction and hydration/fragmentation. Tin hydride-mediated cyclizations of 2-halo-N-(3-methyl-N-sulfonylindole)anilines provide spiro[indoline-3,3'-indolones] or spiro-3,3'-biindolines (derived from imine reduction), depending on the indole C2 substituent. Cyclizations of 2-haloanilide derivatives of 3-carboxy-N-sulfonyl-2,3-dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retro-Claisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles.
منابع مشابه
gem-disubstituent effect: theoretical basis and synthetic applications.
3. Synthetic Applications 1746 3.1. Pericyclic Reactions 1747 3.1.1. Diels−Alder Cycloadditions 1747 3.1.2. Dipolar Cycloadditions 1749 3.1.3. Ene Reactions 1750 3.1.4. Claisen Rearrangements 1750 3.2. Radical Cyclizations 1750 3.3. Transition-Metal-Catalyzed Cyclizations 1753 3.4. Ring-Closing Metathesis 1754 3.5. Electrophilic Cyclizations 1755 3.6. Other Cyclizations 1756 4. Biochemical and ...
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