Stereoselective Intramolecular Oxypalladation of Cyclic 1,3-Dione-Tethered Alkynes

An unconventional, highly stereoselective, and regioselective intramolecular oxypalladation/acyloxylation cascade of alkyne-tethered cyclic 1,3-diones has been developed. This atom-economic Pd(II)-catalyzed annulation reaction is initiated by the oxypalladation of alkyne with an internal carbonyl group via 5-exo-dig cyclization instead of the conventional acetoxypalladation pathway. In this process, the carboxylic acid plays a pivotal role in the generation of an active cationic Pd-complex and the subsequent acyloxylation and proto-demetalation steps. Additionally, this method enables asymmetric cyclization using a chiral bidentate BOX ligand, achieving enantiomeric ratios of ≤93:7.