Enantioselective Synthesis of β-Allenoates via Phosphine-Catalyzed and ZnI<sub>2</sub>-Promoted Preparation of Oxazolidines and Propargylamines Using Chiral Amines, 1-Alkynes, and Propiolates
Diphenylphosphinoethane (DPPE)-catalyzed and ZnI2-promoted in situ formation of oxazolidine, alkynyl zinc, and propargylamine intermediates from 1-alkynes, chiral (S)-diphenyl(pyrrolidin-2-yl)methanol, and propiolates gave the corresponding chiral (R)-β-allenoates in 40–72% yield with up to >99% ee. The intermediate propargylamine was isolated in 50% yield and converted to give the β-allenoate 10aa