Palladium-Catalyzed Synthesis of Substituted Cycloheptane-1,4-diones by an Asymmetric Ring-Expanding Allylation (AREA) «

Palladium-Catalyzed Synthesis of Substituted Cycloheptane-1,4-diones by an Asymmetric Ring-Expanding Allylation (AREA)

Sabrina R. Schulz, Siegfried Blechert*

Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany

This is very similar to Stoltz’s method of Pd-catalyzed deallylation-allyl alkylation of beta-keto allyl ester, except a 4,5-fused substrates containing allyl carbonate at the ring junction were used to study ring expansion reaction. The ketone and carbonate functional groups were strategically positioned to facilitate the allyl alkylation reaction after deallylation with Pd. The reaction was stereoselective because of the chiral phosphine ligand used in the system.

Several examples were demonstrated in the paper. The reaction proceeded in good to excellent yields in all cases. The mechanism is proposed as shown below.