highly functionalized chiralallenesusingchiral N-methylcamphanyl piperazine derivatives is described. In this transformation, chiralpropargylamines are obtained in 79–96% yields with up to 99:1 dr by the CuBr catalyzed reactions of chiralpiperazine derivatives with 1-alkynes and aldehydes containing functional groups, which are converted into chiralallenes in the presence of zinc bromide, affording
Diastereoselective Synthesis of Tetrasubstituted Propargylamines via Hydroamination and Metalation of 1-Alkynes and Their Enantioselective Conversion to Trisubstituted Chiral Allenes
1-alkynes to give the corresponding propargylamine derivatives in up to 94% yield and 99% regioselectivity. The diastereomerically pure chiralpropargylamines were obtained in 23–89% yield using optically active 2-benzyl morpholine and N-methyl camphanyl piperazine. These chiralpropargylamines are readily converted to the corresponding trisubstitued chiralallenes in 71–89% yields with up to 99% ee
was confirmed by single-crystal X-ray analysis of the propargylamines formed. The results are discussed considering mechanisms involving the in situ formation of alkynylzinc halides, followed by diastereoselective addition to chiral iminium ion derivatives to give the corresponding propargylamines, and subsequent conversion to chiralallenes by an intramolecular 1,5-hydrogen shift.