Au-Catalyzed Asymmetric Formal [3 + 2] Cycloaddition of Isocyanoacetates with Maleimides

An efficient protocol for the Au(I)-catalyzed asymmetric formal [3 + 2] cycloaddition of isocyanoacetates with phenylmaleimide has been developed. In the presence of cationic Au(I)/DTBM-segphos complex, excellent diastereoselectivity and high levels of enantioselectivity (up to 97% ee) have been attained with a variety of α-substituted isocyanoacetates. The synthetic potential of the resulting enantioenriched 1-pyrrolines has been demonstrated by the preparation of highly substituted pyrrolidines bearing a quaternary stereocenter.