Stereoselective Synthesis of Pyrrolidines Containing a 3-Fluoro Quaternary Stereocenter via Copper(I)-Catalyzed Asymmetric 1,3-Dipolar Cycloaddition.

A highly efficient asymmetric 1,3-dipolar cycloaddition of azomethine ylides to β,β-disubstituted β-fluoroacrylates catalyzed by a chiral N,O-ligand/Cu(CH3CN)4BF4 system is reported, affording chiral densely substituted pyrrolidines with four contiguous stereocenters, including one fluorinated quaternary stereocenter at the 3-position, in good to excellent yields (up to 99%), with excellent levels of diastereo- and enantioselectivities (dr >20:1; ee up to 99%).