title: Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Hanmo
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: E Ben
authors.initials: EB
authors.lastname: Hay
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Geib
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Curran
keywords: ene-sulfonamide; imine; radical cyclization; radical fragmentation; spiro-indoles