A highly enantioselective [2,3]-Wittig rearrangement of oxindole derived propargylic ethers was realized by using a chiral N,N′-dioxide/NiII complex as catalyst under mild reaction conditions. Various 3-hydroxy 3-substituted oxindoles bearing allenyl groups could be obtained in excellent yields and enantioselectivities (up to 99% yield and up to 99% ee). Moreover, a strong chiral amplification effect was observed, allowing to access enantioenriched products with 15% ee of ligand. The kinetic resolution of racemic oxindole derivatives by a [2,3]-Wittig rearrangement was also realized for the first time in high resolution efficiency and stereoselectivity. This protocol presents a practical approach to synthetically valuable functionalized allenes. Meanwhile, based on the experimental investigations, HRMS analysis as well as X-ray crystal structures of enantiomerically pure and racemic catalysts, it was found that such remarkable chiral amplification effect was attributed to the formation of less active and insoluble racemic L-PiCHPh2/NiII complex.

Nickel(II)-catalyzed asymmetric propargyl [2,3]-Wittig rearrangement of oxindole derivatives: Chiral amplification effect

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.