L-proline catalyzed stereoselective synthesis of (E)-methyl-α-indol-2-yl-β-aryl/alkyl acrylates: easy access to substituted carbazoles, γ-carbolines and prenostodione.

A simple, mild and robust method for the stereoselective synthesis of (E)-methyl α-(3-formyl-1H-indol-2-yl)-β-aryl/alkyl-substituted acrylates via a condensation reaction of methyl 2-(3-formyl-1H-indol-2-yl)acetate with several alkyl or aryl aldehydes using L-proline (25 mol%) as a catalyst is presented for the first time. In addition, completely metal free based high yielding methods for the syntheses of highly substituted biologically important carbazoles, γ-carbolines and the marine alkaloid prenostodione have been developed through our methodology.