RESUMO
A Lewis acid-catalyzed stereoselective [3+2] annulation of crotylsilanes with iminooxindoles is reported to access 2,3'-pyrrolidinyl spirooxindoles with four stereocenters. The addition of NaBArF significantly enhances reactivity, allowing either metal salts or acidic clay to be effective catalysts for the stereoselective reaction.
Assuntos
Indóis/síntese química , Ácidos de Lewis/química , Pirrolidinonas/química , Silanos/química , Compostos de Espiro/síntese química , Catálise , Estrutura Molecular , Oxindóis , EstereoisomerismoRESUMO
We report the Lewis acid catalyzed additions of allylsilanes to N-Boc-iminooxindoles and the formation of novel silicon-containing spirocarbamates via intramolecular trapping of a ß-silyl carbocation by an N-Boc group. Several transformations display the synthetic utility of these spirocarbamate oxindoles, including a reductive cyclization to access new silylated furoindoline derivatives.
Assuntos
Carbamatos/química , Carbamatos/síntese química , Cátions/química , Ésteres do Ácido Fórmico/química , Indóis/química , Indóis/síntese química , Silanos/química , Compostos de Espiro/química , Compostos de Espiro/síntese química , Catálise , Estrutura Molecular , Oxindóis , EstereoisomerismoRESUMO
The condensation cyclization between isatins and 5-methoxy tryptamine catalyzed by chiral phosphoric acids provides spirooxindole tetrahydro-ß-carboline products in excellent yields (up to 99%) and enantioselectivity (up to 98:2 er). A comparison of catalysts provides insight for the substrate scope and factors responsible for efficient catalytic activity and selectivity in the spirocyclization. Chiral phosphoric acids with different 3,3'-substitution on the binaphthyl system and opposite axial chirality afford the spiroindolone product with the same absolute configuration.