Stereoselective Intramolecular Cyclization of Allyl and Homoallyl Benzamide via π-Allylpalladium Complex Catalyzed by Pd(0)

The transformation of acyclic allylic benzamides 4 and homoallylic benzamides 12 to vinyl oxazolines 3 is achieved in the presence of base by the catalysis of Pd(0) in high yield and with high diastereoselectivity. Especially, in the case of homoallylic benzamides 12, trans -oxazolines 3 are formed exclusively or predominantly over cis -oxazolines 8, irrespective of the composition of their stereoisomers. The reaction is believed to proceed via the same π-allylpalladium complex that arises from either primary or secondary allylic acetates. We applied this method to the syntheses of β-amino-α-hydroxy acids 1 and γ-amino-β-hydroxy acids 2, conveniently protected as oxazoline.