Maria-Mar Ortin

First radical addition onto ketenimines: a novel synthesis of indoles

A novel radical-mediated synthesis of 2-alkyl indoles is described. The method is a nonchain process based on the intramolecular addition of benzylic radicals onto the central carbon atom of a ketenimine function, resulting in a 5-exo-dig cyclization.

Intramolecular addition of benzylic radicals onto ketenimines. Synthesis of 2-alkylindoles

The inter- and intramolecular addition of free radicals onto ketenimines is studied. All the attempts to add intermolecularly several silicon, oxygen or carbon centered radicals to N-(4-methylphenyl)-C,C-diphenyl ketenimine were unsuccessful. In contrast, the intramolecular addition of benzylic radicals, generated from xanthates, onto the central carbon of a ketenimine function with its N atom linked to the ortho position of the aromatic ring occurred under a variety of reaction conditions. These intramolecular cyclizations provide a novel radical-mediated synthesis of 2-alkylindoles.

Persistent radical effect in the intramolecular addition of benzylic radicals onto ketenimines: selective cross-coupling of α-(indol-2-yl)benzyl radicals with the 1-cyano-1-methylethyl radical

The intramolecular addition of benzylic radicals, generated from benzyl phenyl selenides by the action of tris(trimethylsilyl)silane and AIBN or AIBMe, onto neighbouring ketenimine functions is studied. The persistent α-(indol-2-yl)benzyl radicals, resulting from such cyclization processes, undergo cross-coupling with the tert-alkyl radicals arising from the thermal decomposition of the AIBN or AIBMe initiators to give, respectively, 3-(1H-indol-2-yl)propiononitriles 10 or propanoates 14. A rare spiropentacyclic compound 17 containing two indole fragments also resulted from one of these radical reactions. The crystal and molecular structures of 10d and 17 have been solved by X-ray analysis.

New Persistent Heteroarylmethyl Radicals Resulting from the Intramolecular Addition of Aryloxymethyl Radicals onto Ketenimines. Synthesis of 2H-1,4-Benzoxazines

A novel method for producing aryloxymethyl radicals, based on the treatment of (phenylseleno)methyl aryl ethers with tris(trimethylsilyl)silane and AIBN is disclosed, as well as the intramolecular addition of such radicals onto C,C-disubstituted ketenimines. The persistent α-(2H-1,4-benzoxazin-3-yl)benzyl radicals resulting from such cyclization processes undergo cross-coupling with the 1-cyano-1-methylethyl radical arising from the thermal decomposition of AIBN to give 2H-1,4-benzoxazines. These radical cyclizations are controlled by the persistent radical effect. The crystal and molecular structure of benzoxazine 10a has been solved by X-ray analysis.