Asymmetric cycloisomerization/[3 + 2] cycloaddition for the synthesis of chiral spiroisobenzofuran-1,3′-pyrrolidine derivatives

An asymmetric catalytic tandem cycloisomerization/[3 + 2] cycloaddition was achieved by a combined system of Au(I) and a chiral N,N′-dioxide–Dy(III) complex. Various enantioenriched 3H-spiroisobenzofuran-1,3′-pyrrolidine derivatives from a number of 2,2′-diester aziridines and 2-ethynyl benzyl alcohols were afforded in moderate to good yields with high diastereo- and enantioselectivities (up to 81% yield, >19 : 1 dr, 95% ee). On the basis of control experiments and the absolute configuration of the product, possible working modes were proposed to understand the origin of chiral control.