Palladium-catalyzed allylation and deacylative allylation of 3-acetyl-2-oxindoles with allylic alcohols

Synthesis of 3-substituted 3-fluoro-2-oxindoles by deacylative alkylation

The fluorination of 3-acetyl-2-oxindoles with N-fluorobenzenesulfonimide under Lewis acid catalysis using Mg(ClO4)2 gives the starting compounds 3-acetyl-3-fluoro-2-oxindoles. These compounds are subjected to base-promoted deacylative alkylation (DaA) for the in situ generation of 3-fluoro-2-oxindole enolates under very mild reaction conditions using Triton B (1 equiv.) and alkyl halides and Michael acceptors as electrophilic reagents. The corresponding 3-alkylated-3-fluoro-2-oxindoles are obtained in good to very high yields. In addition, the palladium-catalyzed deacylative allylation is carried out with allylic alcohols using LiOtBu as the base and 6 mol% of Pd(OAc)2 and dppp, giving the resulting 3-allylated 3-fluoro-2-oxindoles in good yields. This methodology allows a simple synthesis of 3-alkylated-3-fluoro-2-oxindoles, which are difficult to obtain by other routes.

Synthesis of Vinyl Cyclopropanes via Anion Relay Cyclization

A method where an allyl alcohol is formed from a Tsuji-Trost allylation between a vinyl epoxide and an acyl containing nucleophile is described. Subsequently, a retro-Claisen condensation is utilized as a means of through-space anion relay. The anion relay results in the formation of a reactive carbanion and simultaneously activates an allylic alcohol toward intramolecular Tsuji-Trost cyclopropanation. Hence, in one pot, Tsuji-Trost allylation, retro-Claisen activation, and Tsuji-Trost cyclopropanation are combined to access synthetically useful vinyl cyclopropanes from vinyl epoxides using a mild and operationally simple procedure.