Access to 3-Oxindoles from Allylic Alcohols and Indoles

The site-selective and regioselective allylation of 2-substituted indoles was performed by using a ruthenium(IV) precatalyst containing a phosphine-sulfonate chelate. Mono-, di-, and triallylated indoles were selectively obtained depending on the reaction conditions with the formation of water as the only byproduct. The preparation of 3-oxindole derivatives was then successfully performed owing to air oxidation of the corresponding allylated indoles. Diallylated pseudoindoxyls were proven to be good synthons to perform cyclization through a ring-closing metathesis reaction to afford the corresponding tricyclic adducts. The photophysical properties of the 3-oxindoles were measured, and some of the compounds showed strong fluorescence in water.