Chiral phosphorus-based 1,3-dipoles: a modular approach to enantioselective 1,3-dipolar cycloaddition and polycyclic 2-pyrroline synthesis.

The design of a new class of chiral 1,3-dipoles for enantioselective cycloaddition reactions is reported. These phosphorus-based dipoles are easily formed (from imines, acid chlorides, and chiral phosphites), rigidly chiral, and undergo intramolecular alkene cycloaddition with high enantioselectivity. Overall, this provides a straightforward and modular approach to synthesize chiral 2-pyrrolines and pyrrolidines in up to 99% ee.