Reaction of cyclic secondary amines with 1-alkynes and copper(I) chloride at 110-120 °C gives the corresponding alkynylcopper complex, which adds to the iminium ion intermediate formed in situ by hydroamination of 1-alkynes to give the corresponding propargylamine derivatives in up to 94% yield and 99% regioselectivity. The diastereomerically pure chiral propargylamines were obtained in 23-89% yield using optically active 2-benzyl morpholine and N-methyl camphanyl piperazine. These chiral propargylamines are readily converted to the corresponding trisubstitued chiral allenes in 71-89% yields with up to 99% ee upon reaction with ZnBr2 at 120 °C. The results are discussed considering mechanisms involving diastereoselective addition of alkynylcopper complex formed in situ to iminium ions formed in situ regioselectively to produce the corresponding propargylamines, which in turn give the chiral allenes with very high enantioselectivity via an intramolecular 1,5-hydrogen shift in the presence of zinc bromide.

Diphenylphosphinoethane (DPPE)-catalyzed and ZnI-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 in 68% yield and 96% ee upon reaction with ZnI. The results are discussed considering a mechanism involving oxazolidine and iminium ions formed in situ followed by addition of alkynyl zinc complex to produce the propargylamine that gives the corresponding allenoate via a 1,5-hydrogen shift in the presence of ZnI.

The reactions involve the diastereoselective addition of in situ formed alkynylcopper complexes to in situ formed iminium ions regioselectively affording the corresponding propargylamines.

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