Chirality Memory of α-Methylene-π-allyl Iridium Species
Chirality is a type of most important steric information in nature. In addition to central chirality, axial chirality has been catching more and more attention from scientists. However, although many attention has recently paid to the creation of axial chirality and chirality transfer of allenes, no study has been disclosed for the memory of such an axial chirality. The reason is very obvious: the chiral information is stored over three carbon atoms. Here, the first example of memory of chirality (MOC) of allenes has been recorded, which was realized via optically active alkylidene-π-allyl iridium intermediate, leading to highly stereoselective electrophilic allenylation with amines. Specifically speaking, we have established the transition metal-mediated highly stereoselective 2,3-allenylation of amines by using optically active 2,3-allenyl carbonates under the catalysis of a nonchiral iridium (III) complex. This method is compatible with sterically bulky and small substituents on both amines and 2,3-allenyl carbonates and furnish the desired optically active products with high efficiency. Further mechanistic experiments reveal that the isomerization of the optically active alkylidene-π-allyl iridium intermediate is very slow.