Au(I)-Catalyzed Formal Hydroamination of Chiral Allenes to 3-Pyrrolines

Significance

A variety of chiral α-aminoallenes can be converted into chiral 3-pyrrolines in the presence of Au(I) or Au(III) catalysts under mild conditions. When the nitrogen contains a protecting group, slight erosion of enantiopurity is observed; however, with a free amine, complete chirality transfer from axis to center is observed. Mechanistic studies determined that Au(I) is the catalytic species, as the reduction of a Au(III) catalyst to Au(I) was observed in situ with the free amine, and led to cyclization products.