Parallel kinetic resolution of propargyl ketols: formal synthesis of (+)-bakkenolide A

Abstract

We describe an intriguing new example of a parallel kinetic resolution; an asymmetric cyclization–carbonylation of propargyl ketols catalyzed by palladium(II) with chiral bisoxazoline (box) ligands. The 2 S,3 S enantiomer of (±)- 6 was preferentially converted to 13 (45–49% yields, 37–46% ee), and the 2 R,3 R enantiomer of (±)- 6 was preferentially converted to 14 (21–23% yields, 92–97% ee). As an application of this reaction, formal synthesis of (+)-bakkenolide A was achieved.