Direct Access to Chiral β-Fluoroamines with Quaternary Stereogenic Center through Cooperative Cation-Binding Catalysis.

A direct route to chiral β-fluoroamines with tetrasubstituted C-F centers through the organocatalytic Mannich reaction of α-fluoro cyclic ketones and α-amidosulfones by using a chiral oligoethylene glycol as a cation-binding catalyst and KF as a base is reported. For most substrates, nearly perfect enantioselectivities were achieved even at very high temperatures (>80 °C). The salient features of this process include a) a transition-metal-free and operationally simple procedure, b) direct use of α-amidosulfones as bench-stable precursors of sensitive imines, c) direct enolization of racemic α-fluoro cyclic ketones, and d) excellent stereoselectivity up to 99 % enantiomeric excess and >20:1 diastereoselectivity (anti/syn). Thus, this protocol is easily scalable and provides a new approach for the synthesis of biologically relevant products with tetrasubstituted C-F centers. Furthermore, this protocol was also successfully extended to generate C-Cl and C-Br quaternary stereogenic centers.