Synthesis of α-CF-proline derivatives by means of a formal (3 + 2)-cyclisation between trifluoropyruvate imines and Michael acceptors.

We herein report the first formal (3 + 2)-cyclisation between 3,3,3-trifluoropyruvate-derived imines and indandione-based Michael acceptors. This reaction gives access to a novel class of spirocyclic α-CF3-α-proline derivatives with complete control of the diastereoselectivity under phase transfer-catalysed reaction conditions.