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.